Biomedical subjects

F R DeRubertis

Publications and source records attributed to F R DeRubertis.

At least 37 records · Page 2Linked to original sources

PubMed1993

Role for protein kinase C in the mediation of increased fibronectin accumulation by mesangial cells grown in high-glucose medium.

The fibronectin content of RMC cultures grown for 8-14 days in medium containing 30 mM (540 mg/dl) D-glucose was increased 30-60% relative to that of control cells cultured in 10 mM (180 mg/dl) glucose. Addition of equiosmolar concentrations (20 mM, 360 mg/dl) of L-glucose, 3-O-methylglucose, or mannitol to 10 mM glucose media did not alter fibronectin accumulation compared with values observed in 10 mM glucose alone. The basal phosphorylation of the 80,000-M(r) MARKS protein, which is a substrate for PKC, and the phosphorylation induced by acute (15-min) exposure of cells to 15% FCS or to 0.1 microM (50 ng/ml) PDBu were all increased in cells grown in 30 mM compared with 10 mM glucose. By contrast, phosphorylation of the 80,000-M(r) protein in response to a maximal concentration of PDBu (1 microM, 500 ng/ml) was not different in cells grown in 30 mM compared with 10 mM glucose. The acute increases in phosphorylation of the 80,000-M(r) protein were blocked by the PKC inhibitor calphostin C. Chronic (7-day) exposure of mesangial cells grown in 10 mM glucose to 0.1 microM of the PKC agonist PDBu also resulted in a sustained 40% increase in 80,000-M(r) phosphorylation and a 20-30% increase in fibronectin accumulation. As assessed by [35S]methionine incorporation, mesangial cell fibronectin synthesis was increased by exposure to PDBu, a finding consistent with earlier observations with 30 mM glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Alterations in protein kinase C in 1,2-dimethylhydrazine induced colonic carcinogenesis.

Protein kinase C activity and the profile of protein kinase C isozymes alpha, beta, and gamma were examined in subcellular fractions of 1,2-dimethylhydrazine induced colonic adenocarcinomas, surrounding uninvolved colonic mucosa and colonic mucosa from age matched control rats. Responsiveness of colonic mucosal protein kinase C to phorbol dibutyrate induced translocation of the enzyme from the soluble to the particulate cell fraction was also assessed. Although total protein kinase C and specific activities of soluble and particulate enzymes were higher in colonic mucosa of carcinogen treated rats which developed tumors than corresponding values of control mucosa, the subcellular distribution of enzyme activity was not different between uninvolved colonic mucosa of 1,2-dimethylhydrazine treated rats and colonic mucosa of age matched control rats. Thus, evidence for activation of the protein kinase C system of mucosa of the carcinogen treated rats was lacking. Exposure of colonic mucosa from control rats to phorbol dibutyrate induced a clear translocation of enzyme activity from the soluble to the particulate fraction. By contrast, no change in subcellular distribution of protein kinase C activity was noted on exposure of colonic mucosa from 1,2-dimethylhydrazine treated rats to phorbol dibutyrate. Immunoblotting of subcellular fractions of colonic mucosa from control and 1,2-dimethylhydrazine treated rats demonstrated the presence of protein kinase C alpha, but no detectable beta and gamma forms. Total protein kinase C activity and the specific activity of protein kinase C in soluble and particulate fractions was significantly lower in adenocarcinomas compared to uninvolved surrounding mucosa. In contrast to results obtained with colonic mucosa from control and 1,2-dimethylhydrazine treated rats, adenocarcinomas expressed predominantly the beta form of protein kinase C. The alpha form represented less than 10% of the total detectable immunoreactivity in adenocarcinomas. The alterations in protein kinase C isoenzyme expression in tumors and loss of responsiveness of premalignant mucosa to phorbol dibutyrate may be involved in the process of malignant transformation.

1,2-Dimethylhydrazine↗

PubMed1992

Alterations in protein kinase C system of colonic epithelium during fasting-refeeding. Evidence for protein kinase C independent pathway of enhanced proliferative activity.

In the present study, we compared (1) incorporation of [3H]dThd into DNA, (2) total protein kinase C (PKC) activity, (3) the subcellular distribution of PKC, and (4) PKC isozyme (alpha, beta and gamma) mass in colonic mucosal scrapings and isolated superficial and proliferative colonic epithelial cells from 48-hr fasted, 48-hr fasted-refed, and ad libitum-fed rats. Total colonic mucosal PKC activity and PKC alpha mass were higher and the in vivo rate of [3H]dThd incorporation into mucosal DNA was markedly depressed in 48-hr fasted rats compared to ad libitum-fed or fasted-refed rats. These alterations were localized predominantly to the proliferative pool of colonic epithelial cells. Despite an 11-fold increase in mucosal DNA synthesis, no alterations in total mucosal PKC activity were detected in fasted-refed rats compared to rats fed ad libitum. Moreover, no differences in the subcellular distribution of PKC were noted among any of the dietary groups. Intrarectal instillation of deoxycholate activated PKC and increased DNA synthesis 1.5- to 2-fold. Deoxycholate-induced increases in DNA synthesis, but not those induced by refeeding, were inhibited by treatment of rats with the PKC inhibitors H-7, sphingosine, or staurospaurine. The results do not support a role for PKC in the mediation of increased proliferative activity of colonic mucosa induced by refeeding.

Analysis of Variance↗

PubMed1992

Contribution of platelet thromboxane production to enhanced urinary excretion and glomerular production of thromboxane and to the pathogenesis of albuminuria in the streptozotocin-diabetic rat.

Previous studies have demonstrated that urinary thromboxane B2 (TXB2) excretion (UTXB2) and glomerular production of TXB2 are enhanced in experimental diabetes and that selective inhibitors of TX synthesis prevent or delay the development of albuminuria. The present study was conducted to examine the contribution of platelet TXB2 production to the enhancement of UTXB2 and glomerular TXB2 production and to the pathogenesis of albuminuria in the partially insulin-treated moderately hyperglycemic (blood glucose, 200 to 400 mg/dL) streptozotocin-diabetic rat (SDR). Treatment of control rats or of SDR with diabetes of 5 months' duration with antiplatelet serum for 4 consecutive days reduced circulating platelet counts and serum TXB2 generation, an index of platelet cyclooxygenase activity, by 80% or greater, but reduced UTXB2 excretion by only 30%. UTXB2 and glomerular production of TXB2 of thrombocytopenic SDR remained markedly elevated compared with corresponding values from age-matched thrombocytopenic or platelet-replete, nondiabetic controls. Similarly, treatment of rats for 180 days with a dose of aspirin (ASA), which selectively inhibited platelet versus renal cyclooxygenase activity, reduced UTXB2 of both SDR and controls by 25% to 35%. The absolute reductions in UTXB2 induced by either ASA or thrombocytopenia in SDR were significantly greater than the absolute decrements in corresponding controls, suggesting that increased platelet TXB2 production in SDR may contribute to the enhanced UTXB2. However, as in the thrombocytopenic SDR, UTXB2 and glomerular production of TXB2 of SDR treated with ASA remained clearly above corresponding control values. Moreover, chronic ASA treatment failed to prevent the development of albuminuria in SDR.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗

PubMed1992

Thromboxane in the pathogenesis of glomerular injury in diabetes.

The present study examined the role of thromboxane (TX) in the initiation and progression of glomerular injury in diabetic rats, as reflected by albuminuria and glomerular histology. Urinary thromboxane and albumin excretion (UTX and UAlb) were elevated by four months after induction of diabetes in the moderately hyperglycemic (200 to 400 mg/dl glucose) streptozotocin diabetic rat (SDR) compared to age-matched control rats. UTX and UAlb both increased progressively in SDR over the seven month period of study. Glomerular TX production, glomerular volume, fractional and absolute mesangial volume and glomerular basement membrane (GBM) width were also increased after seven months in SDR compared to control. Treatment of SDR with a thromboxane synthetase inhibitor (TXI) 4' (imidazol-l-yl) acetophenone (100 mg/kg/day) for seven months beginning at the time of induction of diabetes prevented the increases in UTX, UAlb, glomerular TX production, glomerular volume and mesangial volume and attenuated, but did not prevent, GBM thickening. When the same dose of the TXI was begun five months after induction of diabetes and continued for two months, UTX and ex vivo glomerular TX production were reduced by only 60% compared to untreated SDR and remained higher than corresponding values in control rats. Delayed treatment with the TXI alone did not alter UAlb compared to untreated SDR. By contrast, treatment of five month albuminuric SDR for only two months with the TXI plus the TX receptor antagonist (TXRA) Bay U3405 (5 mg/kg/day) prevented a further increase in UAlb, and reduced fractional albumin clearance and mesangial volume compared to values in untreated SDR. Combined treatment with the TXI and TXRA had no effect on GBM width or glomerular volume compared to values in untreated SDR. The results support roles for TX in the initiation of, and for TX and/or endoperoxides in the progression of glomerular injury in SDR.

Albuminuria↗

PubMed1992

Effects of aspirin on 1,2-dimethylhydrazine-induced colonic carcinogenesis.

The influence of aspirin (ASA) on 1,2-dimethylhydrazine (1,2-DMH)-induced colonic carcinogenesis was examined in weanling Sprague-Dawley rats. The incidence of adenocarcinomas in response to a single dose of 1,2-DMH was reduced 60% in rats receiving ASA for 1 week before and after the carcinogen. However, ASA had no effect on tumor incidence when initiated 4 weeks after a single dose of 1,2-DMH and continuing until the animals were killed at 36 weeks. The doses of ASA employed suppressed by 95% or more ex vivo colonic prostaglandin E2 (PGE2) production and reduced colonic mucosal cAMP levels in both rats exposed to 1,2-DMH and in age-matched controls. Proliferative activity of colonic mucosa as assessed from tritiated thymidine ([3H]dThd) incorporation into mucosal DNA was increased at 1 week but suppressed by 36 weeks after 1,2-DMH exposure. ASA significantly increased colonic mucosal DNA synthesis, suppressed colonic PGE2 production and reduced mucosal cAMP levels at both 1 and 36 weeks in rats given the 1,2-DMH vehicle. However, ASA failed to alter the enhanced mucosal DNA synthesis observed at 1 week or the suppressed DNA synthesis observed at 36 weeks after a single dose of 1,2-DMH, despite significant inhibition of colonic PGE2 production and reduction in mucosal cAMP levels by ASA. Treatment of rats for 1 week with ASA significantly inhibited basal and arachidonate stimulated decomposition of the 1,2-DMH intermediary metabolite methylazoxy-methanol, assessed ex vivo in colonic mucosal homogenates. Thus, while other mechanisms are not excluded, suppression of 1,2-DMH induced colonic carcinoma by concurrent administration of ASA may be linked in part to altered metabolic activation of this carcinogen via cyclooxygenase-dependent co-oxidation. By contrast, the previously reported suppression of the promotional phase of colonic carcinogenesis in rats by the delayed introduction of cyclooxygenase inhibitors may not be linked to inhibition of local colonic prostanoid production, since (i) inhibition of colonic prostanoid synthesis by ASA did not mimic this antipromotional effect, and (ii) the doses of non-steroidal anti-inflammatory drugs employed in some earlier studies may not significantly inhibit colonic prostanoid synthesis.

1,2-Dimethylhydrazine↗

PubMed1991

Effects of extracellular sodium on cytosolic calcium, PGE2 and cAMP in papillary collecting tubule cells.

An increase in cytosolic calcium (Cai2+), induced by an increase in extracellular calcium concentration or addition of the calcium ionophore A23187, has been shown to suppress basal and AVP responsive cAMP and inhibit water flow in the collecting tubule. In the present study, the relationships between extracellular Na+ concentration, Cai2+, PGE2 and AVP-responsive cAMP production were examined in cultured rat papillary collecting tubule (RPCT) cells. Reducing extracellular Na+ concentration from 144 to 24 mM increased Cai2+ and PGE2 production approximately below 144 mM on Cai2+ or PGE2 was not due to a change in media osmolality or chloride concentration, since these parameters were maintained at constant levels by addition of tetramethylammonium chloride (TMA) or choline chloride. Exposure of RPCT cells to media containing 24 mM Na+ significantly suppressed basal and AVP responsive cAMP compared to that observed at 144 mM Na+. This suppression was mimicked by the calcium ionophore A23187 which also increased Cai2+ and PGE2. The increase in Cai2+ and PGE2 and the suppression of basal and AVP responsive cAMP, which were observed at 24 versus 144 mM Na+, were abolished in calcium free media and were likely due to influx of extracellular calcium. Indomethacin did not prevent the suppressive effects of reducing extracellular Na+ concentration below 144 mM on basal or AVP responsive cAMP, suggesting that the enhanced production of PGE2 did not mediate the reduction in AVP responsiveness. In contrast to cAMP, reductions in extracellular Na+ concentration from 144 to 24 mM did not influence basal cGMP or the cGMP responses to atrial natriuretic peptide or nitroprusside.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Pneumocystis carinii infection presenting as necrotizing thyroiditis and hypothyroidism.

Extrapulmonary Pneumocystis infection has been increasingly reported in patients with acquired immune deficiency syndrome (AIDS), in particular, recently in association with the increasing use of aerosolized pentamidine. This report describes the unusual presentation of extrapulmonary Pneumocystis infection as a thyroid neck mass and clinical hypothyroidism in a 37-year-old man with hemophilia and AIDS. This case differs from the previously reported single case of isolated thyroid pneumocystosis in the presence of a rapidly enlarging neck mass, lack of previous Pneumocystis, and prior prophylaxis with aerosolized pentamidine. The pathologic and electron microscopic description of the peculiar flocculent necrotic thyroid material is contrasted with typical pulmonary alveolar findings in Pneumocystis pneumonia (PCP), the differential diagnoses of a rapidly expanding neck mass, and diagnostic difficulties of hypothyroidism in patients with AIDS are discussed. Finally, it is emphasized that use of aerosolized pentamidine, although successful for prevention of pulmonary PCP, may be insufficient to prevent extrapulmonary infection.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Calcium and prostaglandin E2 in renomedullary interstitial cells.

Renomedullary interstitial cells cultured from the Dahl salt-resistant rat have higher levels of basal cytosolic calcium and prostaglandin E2 and are more responsive to vasopressin than interstitial cells from the Dahl salt-sensitive rat. We examined the potential role of inositol phospholipid hydrolysis in mediating these differences. Vasopressin-induced increases in labeled inositol phosphates were enhanced in renomedullary interstitial cells from Dahl salt-resistant compared with those from salt-sensitive rats. Addition of neomycin reduced basal production of labeled inositol phosphates and abolished the increase in inositol phosphates induced by vasopressin. Neomycin also prevented the peak decline pattern in cytosolic Ca2+ seen with vasopressin but did not influence basal cytosolic Ca2+. In the presence of neomycin, vasopressin induced a modest but prolonged increase in cytosolic calcium. In contrast to its marked effects on inositol phosphate production, neomycin was without effect on basal or vasopressin-responsive prostaglandin E2 production. Moreover, basal and vasopressin-induced increases in cytosolic Ca2+ remained higher in renomedullary interstitial cells from Dahl salt-resistant versus those from salt-sensitive rats exposed to neomycin. The results do not support a requirement for phospholipase C-induced inositol phospholipid hydrolysis in the mediation of vasopressin actions on prostaglandin E2 production by renomedullary interstitial cells and imply that the differences in cytosolic Ca2+ and prostaglandin E2 seen in these two cell lines are not related to differences in inositol phospholipid metabolism.

Animals↗

PubMed1990

Decreased cytosolic calcium and prostaglandin synthesis in prehypertensive rats.

The capacity of cultured renal medullary interstitial cells derived from Dahl salt-sensitive and salt-resistant rats to synthesize prostaglandin E2 (PGE2) was compared. Basal and arginine vasopressin (AVP)-induced PGE2 production by interstitial cells from salt-resistant rats was fourfold to fivefold higher than corresponding values of those from the salt-sensitive rats. Similarly, basal and AVP-responsive release of [3H]arachidonate were twofold higher by interstitial cells from salt-resistant compared with salt-sensitive rats. Differences in PGE2 production were abolished by the calcium inophore A23187 or the addition of exogenous arachidonate. The latter findings suggested a role for altered availability of endogenous arachidonate, possibly mediated by reduced calcium-responsive lipase activity. Basal and AVP-induced increases in cytosolic free calcium concentration, assessed by the aequorin method, were significantly lower in interstitial cells from salt-sensitive versus salt-resistant rats, further supporting a possible role for altered cellular calcium homeostasis. Studies of the potential contribution of various phospholipases and of triglyceride lipase to the release of arachidonate for PGE2 synthesis in interstitial cells implicated phospholipase A2 activity as a major pathway. When assessed in vitro in cell cytosolic fractions at identical calcium concentration, phospholipase A2 activity was lower in interstitial cells from salt-sensitive versus salt-resistant rats. Thus, both reduced cytosolic free calcium and phospholipase A2 activity of interstitial cells from salt-sensitive rats may contribute to the diminished capacity of these cells to liberate endogenous arachidonate for PGE2 synthesis.

Animals↗

PubMed1990

Increase in diacylglycerol mass in isolated glomeruli by glucose from de novo synthesis of glycerolipids.

An increase in glucose concentration in the medium from 5 to 30 mM transiently enhanced diacylglycerol mass and activated protein kinase C in glomeruli isolated from nondiabetic rats as assessed by translocation of enzyme activity from the soluble to particulate fraction. Effects of glucose on both diacylglycerol mass and protein kinase C were evident at 5 and 15 min but waned by 30 min. An increase in glucose concentration in the medium also increased the incorporation of [14C]glucose into the glycerol backbone of diacylglycerol, triacylglycerol, and phospholipids. Several observations implied that [14C]glucose was being incorporated into diacylglycerol through the de novo pathway for glycerolipid synthesis rather than being derived from phospholipids. 1) [14C]glucose incorporation into all the lipids was suppressed by 2-deoxyglucose. 2) The incorporation of [14C]glucose into diacylglycerol and triacylglycerol was evident by 1 min and increased linearly for at least 30 min. In contrast, incorporation into phosphatidylcholine occurred with a lag of at least 5 min. 3) Although only 10% of the [14C]glucose incorporated into lipids was present in diacylglycerol versus greater than 50% in phospholipids, the specific activity of [14C]glucose in diacylglycerol was fivefold higher than that in phospholipid when expressed as a function of mass. 4) Glucose had no effect on labeled diacylglycerol or phosphatidic acid production in glomeruli that had been prelabeled with [3H]glycerol. Glucose-induced increases in diacylglycerol may contribute to the activation of glomerular protein kinase C observed in early diabetes.

Animals↗

PubMed1990

Suppression of urinary albumin excretion in diabetic rats by 4'(imidazol-1-yl) acetophenone, a selective inhibitor of thromboxane synthesis.

Thromboxane contributes to the regulation of glomerular hemodynamics in experimental models of diabetes and has been implicated as mediator in some models of glomerular injury. In the present study we examined urinary albumin, protein, and thromboxane B2 (TXB2) excretion during the 170 days after induction of diabetes by injection of streptozotocin in insulin-treated moderately hyperglycemic (200 to 400 mg/dl glucose) rats (SDRs). The effects of a thromboxane synthesis inhibitor, 4'-(imidazol-1-yl)acetophenone (TXI) (100 mg/kg/day) on these parameters were also assessed. Urinary TXB2 and albumin excretion in SDRs was not different from that in normal rats between 7 and 90 days but were three times higher than normal in SDRs at 125 and 170 days after induction of diabetes. In SDRs, urinary protein excretion was higher than in controls at 170 days but not at earlier time points. Inulin clearance (CIn) of SDRs was significantly higher than control values at 7 and 90 days and was not influenced by TXI during this period. At 170 days CIn was not significantly different in SDRs and normal rats. By contrast, albumin clearance (CAIb) and fractional CAIb were elevated in SDRs when compared with those values in normal rats. Treatment of SDRs with TXI for 170 days completely prevented the rise in urinary TXB2, albumin, and protein excretion, as well as the rise in fractional CAIb, but did not alter prostaglandin E2 (PGE2) excretion. TXI also increased CIn in SDRs to levels that were significantly higher than normal at 170 days. TXI had no significant effect on urinary PGE2, TXB2, albumin, or protein excretion or on CIn in normal rats and did not influence blood pressure or blood glucose in normal rats or SDRs. The results suggest a role for thromboxane in the mediation of albuminuria in the SDR.

Albuminuria↗

PubMed1989

Two-step high-performance liquid chromatography method for the determination of myo-inositol and sorbitol.

A simple two-step HPLC method for the separation and quantitation of myo-inositol and sorbitol in extracts of glomeruli from rat kidneys is described. The limit of detection is 2 ng. The procedure involves fractionation of the sugar alcohols on a Waters Sugar Pak column, preparation of the p-nitrobenzoate derivatives, and further purification with quantitation by absorbance at 254 nm using a Waters mu Porasil column. The applicability of the procedure to determination of sorbitol and myo-inositol in biological samples was demonstrated by the finding of marked alterations in sorbitol and myo-inositol content of glomeruli isolated from diabetic compared to that from normal rat kidneys.

Animals↗

PubMed1989

Sorbinil suppresses glomerular prostaglandin production in the streptozotocin diabetic rat.

Previous studies have suggested a link between hyperfiltration and enhanced polyol pathway activity in the streptozotocin diabetic rat. In the present study we examined the relationship between glomerular sorbitol content, a measure of polyol pathway activity and glomerular filtration rate (GFR), as a function of plasma glucose and time after induction of diabetes. GFR is increased by 1 to 2 weeks in the untreated streptozotocin diabetic rat but falls to values equal to or below control by 2 months. Treatment of diabetic rats with a low dose of insulin to achieve moderate hyperglycemia results in the maintenance of elevated GFR for 2 months. Glomerular sorbitol content in the 1- to 2-week diabetic rats was not significantly different from values in glomeruli from control rats at 1 to 2 weeks but was 11-fold higher than control by 2 months in the untreated diabetic rat. Treatment of diabetic rats with insulin to achieve moderate hyperglycemia resulted in values for glomerular sorbitol content that were not different from control. Thus, elevated GFR was not associated with elevated glomerular sorbitol content in the 1- to 2-week diabetic rat and was dissociated from elevated glomerular sorbitol content in the 2-month diabetic rat. Treatment of 1- to 2-week diabetic rats with sorbinil prevented the rise in GFR observed at this time despite the fact that sorbitol content of glomeruli was not elevated. These results suggested that sorbinil was reducing GFR in the diabetic rat by a mechanism other than aldose-reductase inhibition. The synthesis of vasodilatory prostaglandins by isolated glomeruli and the activity of phospholipase A2 in the particulate cell fraction of glomerular homogenates is higher in 1- to 2-week diabetic rats compared with controls, a finding that may contribute to the elevated GFR in these rats.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1989

Protein kinase C is activated in glomeruli from streptozotocin diabetic rats. Possible mediation by glucose.

Glomerular inositol content and the turnover of polyphosphoinositides was reduced by 58% in 1-2 wk streptozotocin diabetic rats. Addition of inositol to the incubation medium increased polyphosphoinositide turnover in glomeruli from diabetic rats to control values. Despite the reduction in inositol content and polyphosphoinositide turnover, protein kinase C was activated in glomeruli from diabetic rats, as assessed by an increase in the percentage of enzyme activity associated with the particulate cell fraction. Total protein kinase C activity was not different between glomeruli from control and diabetic rats. Treatment of diabetic rats with insulin to achieve near euglycemia prevented the increase in particulate protein kinase C. Moreover, incubation of glomeruli from control rats with glucose (100-1,000 mg/dl) resulted in a progressive increase in labeled diacylglycerol production and in the percentage of protein kinase C activity which was associated with the particulate fraction. These results support a role for hyperglycemia per se in the enhanced state of activation of protein kinase C seen in glomeruli from diabetic rats. Glucose did not appear to increase diacylglycerol by stimulating inositol phospholipid hydrolysis in glomeruli. Other pathways for diacylglycerol production, including de novo synthesis and phospholipase C mediated hydrolysis of phosphatidylcholine or phosphatidyl-inositol-glycan are not excluded.

Animals↗

PubMed1989

Role for local prostaglandin and thromboxane production in the regulation of glomerular filtration rate in the rat with streptozocin-induced diabetes.

We examined the relationship between glomerular filtration rate (GFR), as assessed by inulin clearance, and glomerular prostaglandin and thromboxane production as a function of glycemic control in control rats and rats that had had streptozocin-induced diabetes for 2 months. In severely hyperglycemic (plasma glucose level 644 +/- 40 mg/dl) rats with streptozocin-induced diabetes that had not been treated with insulin, GFR was reduced to values below those in control rats by 2 months, whether data were expressed as milliliters per minute or as a function of kidney weight. By contrast, treatment of the diabetic rats with insulin to maintain moderate hyperglycemia (plasma glucose concentration 398 +/- 40 mg/dl) resulted in a persistent elevation of GFR compared with values in control rats. Basal production of prostaglandin E2 (PGE2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), the stable metabolic product of prostaglandin I2 (PGl2), by glomeruli isolated from the moderately hyperglycemic rats was higher than corresponding values of glomeruli from control rats. Differences in PGE2 and 6-keto-PGF1 alpha production by glomeruli from moderately hyperglycemic and control rats were abolished by addition of arachidonate to the incubation mixture, supporting a role for enhanced availability of arachidonate in the mediation of altered vasodilatory prostaglandin production. By contrast, glomerular production of thromboxane B2 (TXB2), the stable metabolic product of thromboxane A2 (TXA2), was not different in moderately hyperglycemic rats compared with controls. Thus, enhanced production of vasodilatory prostaglandins by glomeruli from moderately hyperglycemic rats was associated with an increase in GFR.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMed1988

Role for protein kinase C in the modulation of glomerular PGE2 production by angiotensin II.

Angiotensin II increased PGE2 release from superfused glomeruli, and stimulated labeled inositol phosphate production. 12-O-Tetradecanoyl phorbol -13-acetate (TPA, 10(-7) M), which stimulates protein kinase C activity in soluble fractions of glomerular homogenates, suppressed angiotensin II actions on inositol phosphate production and PGE2. By contrast, 4a phorbol 12,13 di-decanoate and phorbol had no effect on protein kinase C activity or angiotensin II induced increases in inositol phosphate or PGE2. 1-(5-Isoquinolinyl)-2-methylpiperazine (H-7), which inhibits protein kinase C activity in soluble fractions of glomerular homogenates, prevented TPA induced suppression of angiotensin II actions on inositol phosphate production and PGE2. Moreover H-7 prolonged the time course of angiotensin II induced inositol phosphate production and enhanced angiotensin II actions on glomerular PGE2 production. The results support a role for inositol phospholipid hydrolysis through the phospholipase C pathway in the mediation of angiotensin II actions on PGE2 in glomeruli and are consistent with negative modulation of these actions by protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1988

Sustained increase in the proliferation of rat colonic mucosa during chronic treatment with aspirin.

The effects of indomethacin and aspirin on colonic epithelial proliferative activity, colonic prostaglandin synthesis, and colonic mucosal cyclic adenosine 3',5'-monophosphate content were examined. Administration of indomethacin (3 mg/kg.day, s.c.) for 2 wk suppressed ex vivo colonic prostaglandin E2 production by 50% and increased [3H]thymidine incorporation into mucosal DNA in vivo, but induced colonic inflammation. Higher doses of indomethacin were toxic and associated with high mortality. By contrast, administration of aspirin (50 mg/kg.day, s.c.) for 2-20 wk suppressed colonic prostaglandin E2 production by 97% and was unassociated with colonic inflammation or systemic toxicity. Suppression of colonic prostaglandin E2 production was associated with a sustained stimulation of [3H]thymidine incorporation into colonic mucosal deoxyribonucleic acid (2-20 wk) and an increase in the [3H]thymidine labeling index when examined at 20 wk. Basal cyclic adenosine 3',5'-monophosphate content of colonic mucosa was markedly reduced in aspirin-treated rats. Moreover, addition of dimethyl prostaglandin E2 or 8-Br-cyclic adenosine 3',5'-monophosphate suppressed the elevated levels of [3H]thymidine incorporation into mucosal deoxyribonucleic acid in incubated colonic segments from aspirin-treated rats. The results demonstrate that sustained suppression of colonic prostaglandin synthesis by aspirin is associated with a persistent increase in colonic epithelial proliferative activity. They support a role for local colonic prostaglandin synthesis as a negative modulator of epithelial growth, possibly mediated through increases in colonic mucosal cyclic adenosine 3',5'-monophosphate.

Animals↗