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Biomedical subjects

M E Elliott

Publications and source records attributed to M E Elliott.

At least 19 recordsLinked to original sources
PubMed2003

Metabolic zonation in teleost gastrointestinal tract. Effects of fasting and cortisol in tilapia.

Activities of several metabolic enzymes show distinct patterns of zonation along the intestinal tract of tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss) and copper rockfish (Sebastes caurinus). Zonation is species and enzyme specific, with different metabolic activities concentrated in specific areas, and few generalizations can be made. The rockfish show the smallest degree of zonation, with highest activities in the third quarter of the intestine, and shallow gradients to either side, and a general upswing in activity towards the distal end. In the trout, mitochondrial enzyme activities (citrate synthase, glutamate dehydrogenase, malate dehydrogenase) are highest in the pyloric caeca and decrease along the length of the small intestine. This pattern is accentuated for malic enzyme and glucose 6-phosphate dehydrogenase. These enzymes drop precipitously in activity after the first few sections of the small intestine, while other NADP-linked dehydrogenases (isocitrate dehydrogenase, and 6-phosphogluconate dehydrogenase) show moderate activity in pyloric caeca and peak toward the distal section of the small intestine. In tilapia, glutamate dehydrogenase shows a similar decrease as in trout, but citrate synthase peaks towards the distal sections. NADP-dependent dehydrogenases reveal distinct patterns, peaking in different sections of the intestine-malic enzyme in the proximal midsection, glucose 6-phosphate dehydrogenase in the distal mid-section, and isocitrate dehydrogenase in the anal section. Enzyme activities in the stomach of trout and tilapia also show zonation, with the midsection generally displaying the highest activities. A 5-day treatment of tilapia with an intraperitoneal cortisol deposit (25 mg kg(-1) wet mass) drastically alters metabolic performance along the gut in enzyme specific patterns, generally increasing enzyme activities in site-specific arrangements. Cortisol treatment also leads to the expected increases in activities of phosphoenolpyruvate carboxykinase, pyruvate kinase and aspartate aminotransferase in liver, but not in kidney. Aspartate aminotransferase is the only enzyme in brain significantly increased by cortisol treatment. Short-term food deprivation changes enzyme patterns, often resembling those observed after cortisol administration. We conclude that brain, liver and intestinal amino acid metabolism is an important target for cortisol action in fish and that metabolic zonation is a key factor to be reckoned with when analyzing physiological phenomena in the fish intestine.

Animals↗
PubMed2003

Glutamine synthetase in tilapia gastrointestinal tract: zonation, cDNA and induction by cortisol.

Glutamine synthetase, an enzyme generally associated with ammonia detoxication in the vertebrate brain and with hepatic nitrogen turnover in mammals, shows substantial activities in the gastrointestinal tract of teleostean fishes. Enzyme activity is highest in the central area of the stomach and reveals a distinct distribution pattern in stomach and along the intestine of tilapia (Oreochromis niloticus), rainbow trout (Oncorhynchus mykiss) and copper rockfish (Sebastes caurinus). In all three species, intestinal activity peaks in the distal region of the intestine. The brain contains the highest titre of the enzyme (46 U g(-1) in tilapia brain versus 15 U g(-1) in tilapia stomach), but because of the relative mass of the stomach, the largest glutamine synthetase pool in tilapia body appears to be localized in the stomach. Activities in white and red muscle are very modest at 0.1% of the brain. Independent of distribution, peak activities of glutamine synthetase in selected areas of tilapia stomach and intestine are significantly (two- to fourfold) increased after a 5-day treatment with an intraperitoneal cortisol deposit. Cortisol also increases glutamine synthetase activity in tilapia liver, white and red muscle, while activities in brain remain unaffected. We cloned and sequenced the predominant transcript of tilapia stomach glutamine synthetase (about 1.9 kb), encoding a 371-amino acid peptide. The open reading frame shows considerable identity with glutamine synthetase in toadfish (92% at peptide level, 87% at nucleotide level), but possesses a longer 3'-untranslated region than the toadfish. The tilapia glutamine synthetase mRNA contains a remnant of a putative mitochondrial leader sequence, but without a conserved second site for initiation of translation. We also find evidence for additional transcripts of glutamine synthetase in tilapia, suggesting multiple genes. Finally, we present evidence for similar abundance of glutamine synthetase transcripts in all regions of rockfish intestine. The physiological significance of the presence of glutamine synthetase in teleostean intestine is discussed.

Amino Acid Sequence↗
PubMed2001

Illness intrusiveness among survivors of autologous blood and marrow transplantation.

BACKGROUND: Illness-induced disruptions to lifestyles, activities, and interests (i.e., illness intrusiveness) compromise subjective well-being. The authors measured illness intrusiveness in autologous blood and bone marrow transplantation (ABMT) survivors and compared the results with survivors of solid organ transplants. METHODS: Forty-four of 64 consecutive ABMT survivors referred to the University of Toronto ABMT long-term follow-up clinic completed the Illness Intrusiveness Ratings Scale (IIRS), the Affect Balance Scale (ABS), the Atkinson Life Happiness Rating (ATKLH), the Beck Hopelessness Scale (BHS), and the Center for Epidemiologic Studies Depression (CES-D) Scale. Mean time from ABMT to evaluation was 4.6 +/- 2.8 years. All patients were in remission or had stable disease at the time of evaluation. Autologous blood and bone marrow transplantation patients' IIRS scores were compared with scores reported by recipients of kidney (n = 357), liver (n = 150), lung (n = 77), and heart (n = 60) transplants. RESULTS: Mean IIRS score for the 44 ABMT patients was 37.2 +/- 17 (maximum possible score, 91; minimum possible score, 13). Higher IIRS scores correlated with lower scores on the ABS (r = -0.54; P < 0.0001), and ATKLH (r = -0.44; P = 0.004), and with higher scores on the BHS (r = 0.58; P < 0.0001) and CES-D (r = 0.48; P < 0.0001). The authors compared IIRS scores from the ABMT survivors with scores from recipients of solid organ transplants. Scores were corrected for age, gender, and time from transplant to evaluation. Corrected mean IIRS scores for the marrow (37.5), kidney (38.9), heart (40.0), lung (30.1), and liver (32.3) transplant recipients differed significantly (P < 0.0001 by analysis of covariance). Higher scores among marrow, kidney, and heart transplant survivors were caused by increased scores in the instrumental domain of the IIRS that measures disruptions in health, work, financial situation, and active recreation. CONCLUSIONS: Despite achieving a remission after ABMT, patients continue to experience illness intrusiveness compromising subjective well-being.

Activities of Daily Living↗
PubMed2000

Management of glucocorticoid-induced osteoporosis in male veterans.

OBJECTIVE: To determine whether glucocorticoid-induced osteoporosis in male veterans was managed in accordance with American College of Rheumatology (ACR) guidelines. These guidelines recommend bone mineral density (BMD) determination at the initiation of long-term therapy with prednisone > or =7.5 mg/d, provision of hormone replacement therapy as needed, calcium and vitamin D supplementation as necessary, and antiresorptive therapy for low BMD. DESIGN: Patients receiving prednisone > or =7.5 mg/d throughout a predefined six-month period were identified through a hospital pharmacy database. Electronic and paper chart review was carried out to determine whether BMD measurement by dual-energy X-ray absorptiometry had been performed. Supplemental calcium and vitamin D intake was assessed for each patient. In addition, pharmacy records were reviewed to determine whether antiresorptive therapy was prescribed for patients with low BMD. SETTING: The Wm. S. Middleton Veterans Affairs Medical Center, Madison, WI. RESULTS: Seventy-two men met study criteria. They had been receiving oral prednisone treatment for a median of 30 months (range 6-74); mean daily dosage during the six-month study period was 12.5 mg (range 7.5-37.5). Extensive record review revealed that only six patients (8%) received recommended calcium and vitamin D, and only 43 (60%) had a BMD determination. Of those 43 men, 32 had T-scores below -1, therefore meeting ACR criteria for recommended antiresorptive therapy. However, only 12 of these 32 patients were prescribed antiresorptive therapy. Although this study was not designed to evaluate differences among clinics, there appeared to be better adherence to ACR guidelines for patients cared for in a rheumatology specialty clinic than in other clinics at the institution. CONCLUSIONS: Adherence to ACR guidelines for management of glucocorticoid-induced osteoporosis was poor. Efforts to improve the prevention and management of glucocorticoid-induced osteoporosis in male veterans are warranted.

Adult↗
PubMed1997

Control of cholesterol access to cytochrome P450scc in rat adrenal cells mediated by regulation of the steroidogenic acute regulatory protein.

Cholesterol conversion to pregnenolone by cytochrome P450scc in steroidogenic cells, including those of the adrenal cortex, is determined by hormonal control of cholesterol availability. Intramitochondrial cholesterol movement to P450scc, which retains hormonal activation in isolated mitochondria, is apparently dependent on peripheral benzodiazepine receptor and the recently cloned steroidogenic acute regulatory (StAR) protein. In rat adrenal cells, StAR is formed as a 37-kDa precursor that is transferred to the mitochondrial inner membrane following phosphorylation by hormonally activated protein kinase A, and processed to multiple forms, some of which turn over very rapidly. In bovine cells, StAR undergoes three modifications forming a set of eight proteins seen in both glomerulosa and fasciculata cells. In the former, cyclic AMP and angiotensin II each decrease two forms and elevate six forms. Significantly, the major change seen after activation may not involve phosphorylation of StAR. Cholesterol transfer across mitochondrial membranes is also activated in isolated mitochondria by GTP and low concentrations of Ca2+, apparently prior to activation by StAR. Depletion of StAR by cycloheximide inhibits cholesterol transfer but is overcome by uptake of Ca2+ into the matrix. This activation of cellular cholesterol transport is sustained in adrenal cells permeabilized by Streptolysin O. In rat adrenal cells cAMP elevates 3.5- and 1.6-kb mRNA, hybridized by a 1.0-kb StAR cDNA. A 3.5-kb rat adrenal cDNA that encodes all except the 5' end of the longest StAR mRNA has been characterized. The corresponding gene sequence is distributed across seven exons. The shorter mRNA may arise from polyadenylation signals early in exon 7. However, the 3.5-kb mRNA comprises 80-90% of untreated rat adrenal StAR mRNA and may therefore provide the prime source for in vivo translation of StAR protein.

Adrenal Glands↗
PubMed1997

Angiotensin-responsive adrenal glomerulosa cell proteins: characterization by protease mapping, species comparison, and specific angiotensin receptor antagonists.

Angiotensin II (AngII)-stimulated aldosterone synthesis is mediated by the AngII type 1 (AT1) receptor and requires ongoing protein synthesis. Hormonally-stimulated turnover of a family of 28- to 30-kDa proteins (p30, or steroidogenic acute regulatory proteins) has been linked to enhanced steroid synthesis in several tissues. Our previous work showed that AngII, dibutyryl cAMP, potassium, and atrial natriuretic peptide affected labeling of a group of eight proteins (four of 28 kDa and four of 30 kDa) in bovine adrenal glomerulosa cells. This report extends our findings in three ways: 1) The eight [35S]-methionine-labeled p30 proteins in bovine cells were compared with each other by chymotryptic peptide mapping. Similarity in maps indicated that the eight proteins share a common primary structure. 2) Dibutyryl cAMP treatment of rat adrenal glomerulosa cells affected the levels of four 28-kDa proteins and one 35-kDa protein, whereas AngII affected two of the 28-kDa proteins. There were no responsive 30-kDa proteins in rats comparable with those seen in bovine cells. These results indicate a species difference in the affected proteins. 3) The AT1 receptor antagonist, losartan, inhibited the effects of AngII on aldosterone synthesis and turnover of the p30 proteins in bovine adrenal glomerulosa cells. PD123319, an antagonist specific for the AngII type 2 receptor, did not block AngII-stimulated aldosterone synthesis and had much less effect on p30 protein labeling than did losartan. These results add to the growing body of evidence that this family of p30 or steroidogenic acute regulatory proteins plays a role in the acute regulation of steroidogenesis by a wide variety of stimulatory hormones in several tissues and species. In addition, losartan's inhibition of AngII's effects on the p30 proteins is consistent with a key role for these proteins in processes linking occupation of the AT1 receptor to stimulation of aldosterone synthesis.

Aldosterone↗
PubMed1996

Dibenzoxepinone hydroxylamines and hydroxamic acids: dual inhibitors of cyclooxygenase and 5-lipoxygenase with potent topical antiinflammatory activity.

Hydroxylamine and hydroxamic acid derivatives of a known nonsteroidal antiinflammatory dibenzoxepine series display both cyclooxygenase (CO) and 5-lipoxygenase (5-LO) inhibitory properties. Many of these new dual CO/5-LO inhibitors also exhibit potent topical antiinflammatory activity in the arachidonic acid-induced murine ear edema model. On the basis of their promising profile of in vitro and in vivo activities, hydroxamic acids 24h, 3-(6,11-dihydro-11-oxodibenz[b,e]oxepin-2-yl)-N-hydroxy-N-++ +methylpropanamide (HP 977), and 25, 3-(6,11-dihydrodibenz[b,e]oxepin-2-yl)-N-hydroxy-N- methylpropanamide (P10294), were selected as developmental candidates for the topical treatment of inflammatory skin disorders.

3T3 Cells↗
PubMed1995

Lead increases aldosterone production by rat adrenal cells.

Exposure to lead has been postulated to contribute to elevated blood pressure in humans and has been shown to raise blood pressure in animals. The mechanism of action of lead on blood pressure is unknown. We fed lead to rats in their drinking water and then examined the production of aldosterone by their adrenal cells in vitro. We also measured excretion of aldosterone and corticosterone by intact rats stimulated with corticotropin, with and without lead treatment. At a dose (273 ppm) that raised blood levels to 30 to 40 micrograms/dL, comparable to blood levels in exposed humans, lead induced increased aldosterone secretion in vitro and in vivo. The effect of lead was most evident when cells or animals were stimulated with aldosterone secretagogues. Experiments in vitro indicate that exposure to lead in vivo increases activity of one or more steps in the late pathway of aldosterone biosynthesis. The results suggest that the hypertensive effect of lead involves relative hyperaldosteronism and may be most evident when secretion of this hormone is stimulated.

Adrenal Glands↗
PubMed1993

Fatty acids may regulate aldosterone secretion and mediate some of insulin's effects on blood pressure.

Experiments in vitro and observation made in humans suggest that some unesterified fatty acids (FA) participate, as inhibitors, in the regulation of aldosterone secretion. Removal of FA from adrenal glomerulosa cells with albumin increases the responses to angiotensin II (AII) and dibutyryl cyclic AMP. Micromolar concentrations of some FA including arachidonic, oleic, linoleic, eicosapentaenoic, and docosahexaenoic inhibit aldosterone secretion by adrenal glomerulosa cells. Inhibition is specific--some acids like stearic are inactive, and the adrenal fasciculata is relatively resistant to inhibition. Oleic acid rapidly and reversibly inhibits aldosterone secretion by perfused dog adrenals. Observations in vivo suggest a reciprocal relationship between plasma levels of FA and aldosterone: insulin infusion into dogs lowers plasma FA and increases adrenal responsiveness to All; salt infusions into humans increase plasma FA as aldosterone falls; plasma FA are low in low-renin essential hypertension where adrenal responsiveness to All is high; plasma FA are inversely correlated with ratios of aldosterone to renin in black hypertensives; and plasma FA are high in some seriously ill patients whose aldosterone levels are inexplicably low. All receptors and the final step of aldosterone biosynthesis, oxidation at the 18 position, are the adrenal sites most sensitive to FA. Insulin's antinatriuresis may be mediated in part by its ability to lower plasma FA and thereby enhance adrenal response to secretagogues.

Aldosterone↗
PubMed1993

Mechanism of fatty acid inhibition of aldosterone synthesis by bovine adrenal glomerulosa cells.

Previous work from this laboratory has suggested that the adrenal glomerulosa is under tonic inhibition by fatty acids. The purpose of the present work was to define the mechanism by which fatty acids inhibit aldosterone synthesis. Experiments with isolated bovine adrenocortical cells showed the following. 1) Fatty acids inhibited angiotensin-II-stimulated and (Bu)2cAMP-stimulated aldosterone synthesis with similar potencies. 2) Inhibition of aldosterone synthesis was highly dependent on fatty acid chain length and degree of unsaturation as well as on configuration of double bonds. Oleic acid was the most potent inhibitor among fatty acids prominent in plasma. 3) Cortisol synthesis was less sensitive to oleic acid inhibition than was aldosterone synthesis. 4) Pregnenolone synthesis by angiotensin-II-stimulated adrenal glomerulosa cells was relatively insensitive to oleic acid. 5) For both glomerulosa and fasciculata cells, cortisol synthesis from 21-deoxycortisol, which requires the participation of P450(21), was relatively insensitive to fatty acids. Cortisol synthesis from corticosterone by fasciculata cells, which requires the participation of P450(17) alpha, was also insensitive to oleic acid. These are microsomal enzymes. 6) In glomerulosa cells, aldosterone synthesis from added corticosterone, which requires the 18-oxidase function of P450(11) beta, a mitochondrial enzyme, was potently inhibited by fatty acids; cortisol synthesis from 11-deoxycortisol by glomerulosa cells, which requires P450(11) beta, was less sensitive to inhibition, and cortisol synthesis from 11-deoxycortisol by fasciculata cells was even less sensitive. 7) Aldosterone synthesis from exogenous 18-hydroxycorticosterone was potently inhibited by oleic acid. Thus, fatty acids are potent inhibitors of the 18-oxidase function of the mitochondrial enzyme P450(11) beta, whereas nonmitochondrial steroidogenic enzymes and the 11-hydroxylase function of P450(11) beta are relatively insensitive to fatty acids. The special sensitivity of aldosterone synthesis to fatty acid inhibition appears to result from the unusual susceptibility of the 18-oxidase function of the mitochondrial steroidogenic enzyme P450(11) beta. This mechanism would allow differential regulation of aldosterone vs. cortisol production by unesterified fatty acids.

Albumins↗
PubMed1993

Bovine adrenal glomerulosa and fasciculata cells exhibit 28.5-kilodalton proteins sensitive to angiotensin, other agonists, and atrial natriuretic peptide.

Protein synthesis by bovine adrenal glomerulosa and fasciculata cells in response to various modulators of steroid synthesis was examined using [35S]methionine labeling and two-dimensional gel electrophoresis. Both cell types responded to steroidogenic stimuli with rapid changes in a family of 28- to 30-kilodalton (kDa) proteins similar to those described in rat fasciculata by Epstein and Orme-Johnson. In glomerulosa, angiotensin-II (AII), potassium, and (Bu)2cAMP stimulated the appearance of two 28.5-kDa proteins (no. 3 and 4) with pI values of 6.44 and 6.33 and decreased labeling of two other 28.5-kDa proteins (no. 1 and 2) with pI values of 6.9 and 6.59. The rank order of potency on aldosterone synthesis and that on proteins 1-4 were the same: (Bu)2cAMP > AII > potassium. Atrial natriuretic peptide blocked the effects of AII on all four proteins and on aldosterone synthesis. Adrenal secretagogues also affected labeling of four slightly larger (30 kDa) proteins (no. 5-8). Corresponding proteins in each quartet are separated by the same difference in isoelectric points. These eight proteins may represent a core protein systematically modified in a number of ways. Aldosterone synthesis in glomerulosa, like glucocorticoid synthesis in fasciculata, requires ongoing protein synthesis. The 28- to 30-kDa proteins increased by steroidogenic stimuli in both cells and decreased by atrial natriuretic peptide in glomerulosa may be the proteins whose synthesis is crucial to acute control of steroidogenesis. Our results indicate that these proteins are made in response to calcium- or calcium/phosphoinositide-dependent mechanisms as well as by cAMP.

Angiotensin II↗
PubMed1992

Insulin-stimulated glucose transport in circulating mononuclear cells from nondiabetic and IDDM subjects.

The objectives of this study were 1) to evaluate glucose transport and its regulation by insulin in easily accessible human cells, 2) to investigate the glucose transporter isoforms involved, and 3) to establish whether a defect in glucose transport is associated with peripheral insulin resistance, which is common in insulin-dependent diabetes mellitus (IDDM) patients. We measured 2-deoxyglucose (2-DG) uptake in circulating mononuclear cells from 23 nondiabetic adults, 16 adults with IDDM, and 10 children with IDDM. Circulating mononuclear cells were separated from whole blood by Ficoll gradients and incubated with +/- 1 nM insulin. 2-DG uptake was measured after incubation with [3H]2-DG and cell separation through corn oil-phthalate. Cytochalasin B-inhibitable 2-DG uptake (basal and insulin stimulated) was higher in control than in IDDM subjects (P less than 0.001). Insulin significantly increased 2-DG uptake or 3-O-methylglucose uptake in both groups. Basal and insulin-stimulated 2-DG uptake was similar for adults and children with IDDM and did not correlate with age or body mass index in any group or disease duration, insulin dosage, or HbA1c in IDDM. In separated monocytes and lymphocytes, 2-DG uptake increased in response to insulin only in the monocyte population. Insulin dose-response curves indicated maximal stimulation of hexose uptake at 1-2 nM insulin for both control and diabetic subjects and demonstrated a significant decrease in maximal insulin response in the latter. Immunoblotting with specific antibodies revealed that circulating mononuclear cells and separated monocytes express the GLUT1 but not the GLUT4 isoform of the glucose transporter.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Sphingosine inhibits angiotensin-stimulated aldosterone synthesis.

Sphingosine and other protein kinase C inhibitors were tested for their ability to inhibit aldosterone synthesis by bovine adrenal glomerulosa cells. Sphingosine inhibited angiotensin (AII)-stimulated aldosterone synthesis (IC50 of 5 microM). At doses that totally blocked steroidogenesis, sphingosine did not affect protein synthesis or [125I]AII binding to cells. Sphingosine also inhibited dibutyryl cyclic AMP (dbcAMP)-stimulated aldosterone synthesis. Sphingosine inhibited pregnenolone synthesis from cholesterol, but not the conversion of progesterone or 20 alpha-hydroxycholesterol to aldosterone. These results suggest that sphingosine inhibits steroidogenesis at a locus close to that where stimulation occurs by AII and dbcAMP. Other protein kinase C inhibitors were tested. Retinal, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), and staurosporine inhibited aldosterone synthesis stimulated by AII and dbcAMP. Retinal and H-7 also inhibited progesterone conversion to aldosterone, and retinal blocked [125I]AII binding. Staurosporine was more specific, inhibiting AII-stimulated aldosteronogenesis at concentrations which had little effect on conversion of progesterone to aldosterone. Because they inhibited dbcAMP stimulation, none of the inhibitors was sufficiently specific to use as a probe of the role of protein kinase C. The IC50 of sphingosine suggests that this or related products of lipid hydrolysis could act as endogenous regulators of adrenal cell function.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Fatty acids are potential endogenous regulators of aldosterone secretion.

Adrenal glomerulosa cells washed with delipidated albumin produced increased amounts of aldosterone in response to angiotensin-II (AII) or (Bu)2cAMP. Albumin treatment also increased binding of 125I-labeled AII to high affinity binding sites on adrenal cells. Lipid extracts of albumin solutions that were used to wash cells inhibited AII binding and aldosterone responses by washed glomerulosa cells. Chromatographic fractionation and mass spectroscopic analysis indicated that the inhibitors removed from cells by albumin were long chain fatty acids. Exogenous fatty acids not only inhibited AII binding, but they inhibited basal aldosterone production and increments in aldosterone caused by AII or dbcAMP, suggesting an effect on postreceptor steps in aldosteronogenesis. The most potent and most abundant fatty acids removed from adrenal cells were oleic, linoleic, and arachidonic. These fatty acids inhibited at micromolar concentrations in the absence of albumin and at somewhat higher concentrations in its presence. Cells that had been washed, then inhibited by exogenous oleic acid in vitro, were restored to their enhanced responsiveness by a second albumin wash, making it unlikely that cell damage is the mechanism of inhibition by fatty acids. Responses of fasciculata cells were not potentiated by albumin washes, and cortisol production was less sensitive than aldosterone production to exogenous fatty acids. Binding of ANP to glomerulosa cells was not affected by albumin or fatty acids. These results combined with clinical correlations make it plausible that unesterified fatty acids are naturally occurring regulators of the adrenal glomerulosa. Insulin's ability to lower plasma levels of fatty acids may be one way that it causes sodium retention.

Aldosterone↗
PubMed1990

Phosphorylation of adrenal histone H3 is affected by angiotensin, ACTH, dibutyryl cAMP, and atrial natriuretic peptide.

Angiotensin (AII) and atrial natriuretic peptide (ANP) exert opposite effects on phosphorylation of a 17.6 kDa nuclear protein from bovine adrenal glomerulosa cells. The protein was separated by sodium dodecyl sulfate electrophoresis and blotted onto polyvinylidene difluoride, and the N-terminal sequence was obtained. This sequence corresponded to histone H3. Another polyacrylamide gel electrophoresis system was used to confirm that AII stimulated the phosphorylation of histone H3. ACTH[1-24] stimulated phosphorylation of the same protein. Dibutyryl cAMP stimulated phosphorylation of a 17.6-kDa protein, and two gel electrophoresis systems confirmed that the protein affected was histone H3. In situ peptide mapping using papain, of either purified standard histone H3 or of the adrenal 17.6-kDa protein, produced the same major fragment as observed by silver staining. Therefore, the 17.6-kDa protein that is affected by AII, ANP, ACTH, and dibutyryl cAMP is histone H3. This finding suggests that in addition to their mutually antagonistic effects on acute steroidogenesis, AII and ANP may exert opposite effects on adrenal cell functions involving the nucleus.

Adrenocorticotropic Hormone↗
PubMed1990

Analysis of angiotensin II binding to human platelets: differences in young and old subjects.

We examined the binding of radiolabeled angiotensin II (AII) to human platelets to characterize the apparent increase in AII receptors observed in older subjects. At 22 degrees C, the amount of radioactivity associated with platelets from older subjects increased continuously for more than 2 hours. The same amount of radioactivity was displaced by addition of unlabeled AII at 30 min and 60 min. In the presence of phenylarsine oxide, in the cold, or when labeled antagonist was the ligand, binding came to equilibrium by 30 min. High pressure liquid chromatography demonstrated that 125I-AII was the major radioactive compound in the supernatant and platelets after incubation, but the platelets also contained radiolabeled AII fragments. Thus, some degradation accompanied interaction of AII and platelets. Phenylarsine oxide did not prevent degradation of bound AII, suggesting that degradation precedes internalization. On average, maximum binding was greater in older subjects whether platelets were incubated with 125I-AII alone, with 125I-AII and phenylarsine oxide to prevent internalization, or when the competitive inhibitor 125I-sar1,ile8-AII was the radioligand. Variability of binding among subjects also increased with age. Thus, platelets bind, degrade, and internalize AII, and the three processes occur to a greater extent in platelets from some, but not all older subjects.

Adult↗
PubMed1990

Ionophores for monovalent cations inhibit angiotensin-stimulated aldosteronogenesis.

We examined the effects of monensin (a sodium ionophore), valinomycin (a potassium ionophore), and nigericin (a nonspecific ionophore) on steroid production and its stimulation in bovine adrenal glomerulosa and fasciculata cells. All three ionophores at nanomolar concentrations inhibited angiotensin (AII)-stimulated aldosterone production; potassium-stimulated aldosteronogenesis was more sensitive, and cortisol synthesis by fasciculata cells was much less sensitive. Ionophores completely inhibited the early pathway of aldosteronogenesis and partially inhibited conversion of progesterone to aldosterone. Ionophores had no effect on pregnenolone production by isolated glomerulosa mitochondria. Monensin had no effect on AII binding, calcium flux, calcium transient, protein phosphorylation, or protein synthesis; valinomycin slightly inhibited these processes. Valinomycin lowered cell potassium and raised cell sodium, but its inhibition of aldosteronogenesis was not overcome by increasing extracellular potassium. Monensin and nigericin had no effect on cell potassium or sodium. Cellular ATP was decreased by valinomycin, but not by monensin or nigericin. Our results show that stimulation of aldosteronogenesis by AII and potassium is highly sensitive to ionophores of monovalent cations. Monensin and nigericin inhibit steroidogenesis at concentrations that have no other observed deleterious effects on glomeulosa cells. These results identify a distinguishing characteristic of adrenal glomerulosa cells and suggest a new pharmacologic approach to inhibition of aldosteronogenesis.

Adenosine Triphosphate↗