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T Inagami

Publications and source records attributed to T Inagami.

At least 109 records · Page 6Linked to original sources
PubMed1992

Identification and characterization of a new binding site for angiotensin II in mouse neuroblastoma neuro-2A cells.

Specific binding site for 125I-angiotensin II (Ang II), with unique pharmacological properties uncommon to the hitherto recognized receptor subtypes, was observed in mouse neuroblastoma cells (Neuro-2A). Differentiation of the cells with 100 nM PGE1 resulted in a 10-fold increase in the number of Ang II binding sites without changing the binding affinity (Kd value: 12.0 nM). 125I-Ang II binding to membranes of differentiated Neuro-2A was inhibited by unlabeled Ang II with a Ki value of 7.06 +/- 1.09 nM but not by Ang III (1 microM). Both AT1 antagonist, Dup753, and AT2 antagonist, PD123319, failed to inhibit 125I-Ang II binding at 1 microM. 125I-Ang II binding was not affected by GTP analogs such as GTP gamma S and Gpp(NH)p. These results suggest that Neuro-2A cells possess a binding site for Ang II which is different from the presently known subtypes of Ang II receptors, and that the number of the binding site is regulated by cell differentiation.

Angiotensin II↗
PubMed1992

Endothelin-1 receptor antagonist: effects on endothelin- and cyclosporine-treated mesangial cells.

Endothelin-1 (Et) has profound effects on glomerular microcirculation and mesangial cell contraction. A parameter of mesangial cell contraction was examined by measuring myosin light chain phosphorylation (MLCP) in glomerular mesangial cells in the presence and absence of a newly developed endothelin-1 receptor antagonist (EtA). Addition of Et alone (10 nM) caused a marked increase in MLCP, which, on average, rose by 53 +/- 6% above the level in cells exposed to vehicle (P less than 0.0005). This effect was shown to continue for at least one hour; MLCP at 60 minutes was 64 +/- 12% higher than controls, (P less than 0.025), constituting a unique observation of an in vitro parameter which parallels the characteristic in vivo effect of Et. Treatment of cells with EtA virtually abolished this Et-induced increase in MLCP, which rose by only 2 +/- 3% and -1 +/- 4% for doses of EtA of 44 nM and 66 nM, respectively. Examination of the intracellular calcium concentration, [Ca2+]i, revealed that EtA almost completely abolished the transient increase in [Ca2+]i evoked by Et and also suppressed the early portions of the sustained increase in [Ca2+]i. EtA was ineffective in abolishing [Ca2+]i increase in response to arginine vasopressin. Finally, to evaluate EtA's efficacy in a pathophysiologic setting, we also studied mesangial cells exposed to cyclosporine (Cs). Exposure of mesangial cells to Cs (10(-5) M) for 60 minutes caused a significant increase in MLCP, on average, by 38 +/- 6% above control (P less than 0.0005), while cells exposed to Cs in the presence of EtA increased MLCP significantly less, by only 15 +/- 9%. These data provide further evidence for Et's long-lasting cellular actions, and demonstrate inhibitory effects of an Et receptor antagonist after direct cellular exposure to Et and also after Cs exposure, a pathophysiologic setting which likely involves Et.

Amino Acid Sequence↗
PubMed1992

Synthesis of renin by tubulocystic epithelium in autosomal-dominant polycystic kidney disease.

Evidence suggests an important role for the renin-angiotensin system in the pathogenesis of autosomal-dominant polycystic kidney disease (ADPKD). Therefore, we studied the presence of immunoreactive renin in renal biopsies and measured the concentrations of renin in cyst fluids. Normal kidneys and kidneys with renal artery stenosis were used for comparison. In ADPKD, immunoreactive renin was present in juxtaglomerular apparatus, associated arterioles, and in some cells within the connective tissue surrounding the cysts. Vascular immunoreactive renin was less prominent than in renal artery stenosis. Increased amounts of tubular immunoreactive renin were noted in polycystic kidneys, as compared to normal kidneys and kidneys with renal artery stenosis. Cyst fluids contained renin detected by Western analysis and enzymatic activity; concentrations were greater in gradient cysts than in nongradient cysts. Seventy-four percent of the renin in gradient cysts was active as compared to 23% in nongradient cysts and 15% in plasma. To determine whether cyst epithelial cells are capable of synthesizing renin, these cells were isolated in tissue culture. Enzymatic assay of extracts from these cells revealed the presence of renin-like enzymatic activity (1.3 +/- 0.8 ng AI/mg protein/hr). The synthesis of renin by tubulocystic epithelium was confirmed by [35S]-methionine radiolabeling of cyst-derived cells, followed by immunoprecipitation and SDS-PAGE and by detection of renin mRNA by the polymerase chain reaction. These results indicate that the tubulocystic epithelium has the potential to synthesize renin. Elevated levels of active renin in renal cysts may be linked to the pathogenesis of hypertension in ADPKD. The occurrence of renin in the lining epithelium of cyst walls raises the possibility that abnormal expression of the renin-angiotensin system may, by a paracrine or autocrine mechanism, regulate epithelial hyperplasia in growing renal cysts.

Base Sequence↗
PubMed1992

Endothelin receptor antagonism is protective in in vivo acute cyclosporine toxicity.

Endothelin (Et) has been implicated in cyclosporine A (CsA) nephrotoxicity. We have previously shown that CsA treatment in rats results in up-regulation of Et receptors specifically within the kidney. The role of Et in vivo CsA nephrotoxicity was therefore studied further with a new competitive antagonist, BQ-123, specific for Et(A) receptors (EtRA). Systemic administration of CsA in Munich-Wistar rats resulted in marked glomerular hypoperfusion and hypofiltration, with RPF in left and right kidneys falling by some 40% to 1.60 +/- 0.25 and 1.73 +/- 0.38 ml/min and GFR decreasing by some 20% to 0.61 +/- 0.05 and 0.67 +/- 0.11 ml/min, respectively. Selective infusion of EtRA into the left renal artery following systemic CsA treatment had no effect on this hemodynamic pattern (RPF 1.58 +/- 0.29 and 1.92 +/- 0.34 ml/min and GFR 0.60 +/- 0.09 and 0.70 +/- 0.08 ml/min in left and right kidneys, respectively, P = NS vs. CsA period). By contrast, intrarenal infusion of EtRA prior to systemic administration of CsA resulted in a strikingly different pattern of renal hemodynamics. Thus, EtRA pretreatment in the left kidney protected against glomerular dysfunction following CsA: RPF was maintained, 3.23 +/- 0.28 ml/min versus 2.96 +/- 0.31 (P = NS EtRA vs. EtRA + CsA), as was the GFR, 1.04 +/- 0.16 ml/min versus 1.12 +/- 0.09 (P = NS). However, the contralateral right kidneys of these rats, not pretreated with EtRA, showed no protective effect: RPF decreased from 3.15 +/- 0.34 ml/min to 2.39 +/- 0.19 and GFR from 1.04 +/- 0.10 ml/min to 0.85 +/- 0.07 (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Identification of a candidate gene responsible for the high blood pressure of spontaneously hypertensive rats.

OBJECTIVE: We have recently isolated a gene, designated as the SA gene, which is more than 10 times more abundantly expressed in the kidneys of spontaneously hypertensive rats (SHR) than in those of Wistar-Kyoto (WKY) rats. To address the issue whether the SA gene is one of the genes responsible for the hypertension of SHR, a genetic cosegregation analysis of the blood pressure values with the genotypes in an F2 rat population was undertaken in this study. METHODS AND DESIGN: Male F2 rats were bred from SHR and WKY rats. The genotypes of the SA gene of the F2 rats were determined by utilizing the StuI restriction fragment length polymorphism of the SA gene between SHR and WKY rats. The blood pressure values were determined by the tail-cuff method. The effect of the genotype of the SA gene on the blood pressure of the F2 rats was analysed by one-way analysis of variance. RESULTS AND CONCLUSION: The blood pressure of the F2 rats inheriting two SHR alleles of the SA gene was significantly higher than that of the F2 rats inheriting two WKY alleles. This indicates that the SA gene, or a gene closely linked to it, has a capacity to influence the blood pressure values of the F2 rat population. Further studies to identify functions of the SA gene products will be necessary.

Animals↗
PubMed1992

Renin and angiotensinogen expression during the evolution of diabetes.

The expression of renin and angiotensinogen genes and their proteins were studied during the progression of diabetes using adult BioBreeding spontaneously diabetic rats at 1 day and 2-12 months of diabetes. The number of renin-stained cells per juxtaglomerular apparatus was determined by immunocytochemistry. Initially, at 2 months of diabetes the number of renin-stained cells per juxtaglomerular apparatus increased significantly (p less than 0.0001, 2 months versus resistant groups) and was followed by a decrease in the number and intensity of renin-stained cells after 12 months of diabetes (p = 0.007, 2 months versus 12 months). A significant negative correlation was observed between the number of renin-containing cells and the duration of diabetes (r = 0.99, p = 0.014). Immunoreactive angiotensinogen was restricted to the proximal tubule and appeared increased after 4 and 8 months of diabetes as compared with the 2- and 12-month diabetic groups. Renin messenger RNA (mRNA) levels increased with the onset of diabetes and decreased markedly during chronic diabetes. At 1 day of diabetes, renin mRNA levels were 700% higher than at 12 months of diabetes. Angiotensinogen mRNA levels were unchanged. We conclude that diabetes results in an initial increase in renin gene expression, and as the duration of diabetes lengthens, there is a progressive decrease in renin gene expression and in the number of cells containing renin. These findings suggest that as the duration of diabetes and the age of the animal lengthens, there is a decrease in the number of cells expressing the renin gene.

Angiotensinogen↗
PubMed1992

Localization of components of the renin-angiotensin system within the kidney and sustained release of angiotensins from isolated and perfused kidney.

We found colocalization of renin, angiotensin (Ang) I and Ang II in juxtaglomerular (JG) cells of the kidney. Coexistence of Ang II in renin granules was demonstrated by electron microscopic immunogold labeling of these components. Coexistence of both Ang I and Ang II in the high density renin storage granules were also demonstrated by gradient centrifugation of renal homogenate. These findings supported the synthesis of Ang I and Ang II in juxtaglomerular cells. Isolated and cultured JG cells showed the synthesis of Ang I, Ang II and renin. Ang I and Ang II were secreted from isolated and perfused rat kidneys at steady rates over 2 hr. Their secretion rates were proportional to that of renin. The rate of Ang II secretion from the kidney was higher than that from the vascular bed. Ang II was also found in renal lymph. These findings indicate that a large amount of Ang II is generated in JG cells by the intracellular action of renin and may play a significant role in the regulation of renal function.

Angiotensins↗
PubMed1992

Quantitative analysis of renin gene expression in extrarenal tissues by polymerase chain reaction method.

OBJECTIVE: To evaluate the significance of locally synthesized renin in the pathogenesis of hypertension, we investigated modulation of the renin gene expression in extrarenal tissues. DESIGN: Expression levels of renin messenger (m)RNA in various tissues were determined in the genetically hypertensive rats and their control strains. Effects of salt, captopril and clonidine upon renin gene expression were also investigated. METHODS: Due to the very low expression level of renin mRNA in extrarenal tissues, a competitive polymerase chain reaction method of assessment was applied. Total RNA from various tissues combined with a synthetic deletion-mutated renin RNA were reverse-transcribed and the resultant complementary DNA mixtures were amplified in one reaction in which the same primers were used. RESULTS: Expression levels of the renin mRNA in various parts of the central nervous system of 4-week-old spontaneously hypertensive rats were approximately twofold higher than those of age-matched Wistar-Kyoto rats and expression levels in the brain were positively modulated by the administration of either captopril or clonidine. CONCLUSIONS: The importance of the brain renin angiotensin system in the pathogenesis of hypertension in spontaneously hypertensive rats was strongly suggested.

Adrenal Glands↗
PubMed1991

Phospholipase D in cultured rat vascular smooth muscle cells and its activation by phorbol ester.

We determined the phospholipase D (PLD) activity in rat vascular smooth muscle cells by the formation of phosphatidylethanol in cells prelabeled with [3H] myristic acid. The enzyme was markedly activated by a phorbol ester (TPA). Down regulation of protein kinase C (PKC) resulted in almost complete inhibition indicating PKC-dependent mechanism of its activation. Depletion of calcium by EGTA and TMB-8 caused 53% inhibition. Chelator-stable association of PKC to membrane by TPA was observed in the absence of extracellular Ca2+. The mitogenic peptide PDGF also caused a marked stimulation of PLD. These results indicate that PLD in vascular smooth muscle cells is stimulated by TPA through the activation of PKC both by calcium-dependent and independent mechanisms.

Animals↗
PubMed1991

Rat angiotensin II receptor: cDNA sequence and regulation of the gene expression.

The nucleotide and amino acid sequences for rat type I angiotensin II receptor were deduced through molecular cloning and sequence analysis of its complementary DNAs. The rat angiotensin II receptor consists of 359 amino acid residues and has a sequence similar to G protein-coupled receptors. The expression of this receptor gene was detected in the adrenal, liver and kidney by Northern blotting. Sodium deprivation positively modulated the expression of the receptor gene in the adrenal. No detectable change was observed in the expression levels of this receptor gene between spontaneously hypertensive rats and Wistar-Kyoto rats in the tissues examined including the adrenal, brain, kidney and liver. Interestingly the expression of this receptor gene was developmentally regulated.

Amino Acid Sequence↗
PubMed1991

Cloning and expression of a complementary DNA encoding a bovine adrenal angiotensin II type-1 receptor.

Angiotensin II elicits different responses which affect cardiovascular, neuronal and electrolyte transport regulation. To understand the mechanisms responsible for its various actions, the receptor for angiotensin II has long been sought, but numerous attempts to purify the receptor have been unsuccessful owing to its instability and low concentration. We report here the expression cloning of a complementary DNA encoding a bovine angiotensin II receptor to overcome these difficulties. The receptor cDNA encodes a protein of 359 amino-acid residues with a transmembrane topology similar to that of other G protein-coupled receptors. COS-7 cells transfected with the cDNA expressed specific and high-affinity binding sites for angiotensin II, angiotensin II antagonist and a non-peptide specific antagonist for type-1 receptor. Dithiothreitol inhibited ligand binding. The concentration of intracellular Ca2+ and of inositol-1,4,5-trisphosphate increased in the transfected COS-7 cells in response to angiotensin II or angiotensin III, indicating that this receptor is the type-1 receptor for angiotensin II. Northern blot analysis revealed that the messenger RNA for this receptor is expressed in bovine adrenal medulla, cortex and kidney.

Adrenal Cortex↗
PubMed1991

Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney.

The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques 1) to identify possible sites of synthesis; 2) to compare the localization of ANP to known physiological effects; 3) to determine species differences, if any, in ANP localization; and 4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP, IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.

Amino Acid Sequence↗
PubMed1991

Effect of progesterone on renin secretion in endometrial stromal, chorionic trophoblast, and mesenchymal monolayer cultures.

Renin messenger ribonucleic acid expression has been shown in decidual tissue and endometrium, but weakly in chorion laeve, suggesting decidua as a primary source of uteroplacental renin. We proposed to confirm active renin secretion by endometrial stromal cells and examined the effect of progesterone-induced decidualization on secretion. Separate monolayer cultures of endometrial stroma, trophoblast, and mesenchymal cells were established and maintained for 10 to 15 days. Active renin concentration was measured with radioimmunoassay for angiotensin I generation and expressed as picograms per milliliter of angiotensin I generation per 10(5) cells. Active renin concentration was high in control secretory endometrial stromal cells (513 pg/ml) compared with trophoblast (none) and mesenchymal cell cultures (74 pg/ml). Marked decrease in active renin secretion occurred in control endometrial stromal cells (days 13 to 15, 86 pg/ml), whereas progesterone-induced decidualization sustained and increased secretion (days 13 to 15, 1017 pg/ml). This renin activity was quantitatively inhibited in culture fluid assays by specific human renal renin antibody in serial dilutions. Renin activity measurements before and after trypsin activation showed the majority of renin (91.15%) in the inactive form and a smaller fraction (8.85%) in the active form. Immunohistochemistry with the use of specific human renal renin antibody confirmed the presence of renin and its stimulation by progesterone in endometrial stromal cells. Progesterone had minimal effect on mesenchymal cells. These data confirmed endometrial stromal cells as a significant source of active renin and showed that progesterone induced a marked increase in this production.

Chorion↗
PubMed1991

Glomerular renin synthesis and storage in the remnant kidney in the rat.

The intrarenal renin-angiotensin system can exert local control of the nephron and its circulation. In the subtotally nephrectomized model of chronic renal disease in the rat, angiotensin appears to play a prominent role in glomerular function. Glomeruli in this model demonstrate greater staining for intraglomerular renin by immunofluorescence microscopy than do those in control rats. Glomeruli from remnant nephrons contain increased renin content. Also, glomeruli from remnant nephrons contain an increased proportion of the mRNA for renin. Adriamycin-induced nephrosis did not evoke the same degree of renin staining and did not lead to increased glomerular expression of the renin gene, findings that argue against permselective defects and glomerular trapping as the sole cause of the glomerular renin in the remnant kidney model. Thus, renin synthesis and accumulation occur in the remnant glomerulus and this migration may underlie in part the dependence of glomerular function on the renin-angiotensin system in this model.

Animals↗
PubMed1991

Roles of renal and vascular renin in spontaneous hypertension and switching of the mechanism upon nephrectomy. Lack of hypotensive effects of inhibition of renin, converting enzyme, and angiotensin II receptor blocker after bilateral nephrectomy.

Inhibitors of angiotensin converting enzyme, renin, and the angiotensin II (Ang II) receptor lower the blood pressure of spontaneously hypertensive rats (SHR) used as a model of essential hypertension. Since their plasma renin levels were normal or subnormal, renin in the vascular tissue was considered to play a key role in the maintenance of the hypertension. To clarify the source and localization of renin in SHR, antirenin antibodies, the converting enzyme inhibitors delapril, enalapril, and the Ang II receptor antagonist DuP 753 were administered to intact and bilaterally nephrectomized SHR and their normotensive controls. The efficient hypotensive action of the renin antibody indicated that renin of renal origin is a dominant factor. Gradual but complete disappearance of antihypertensive action of these inhibitors of the renin-angiotensin system upon bilateral nephrectomy indicated the importance of membrane-associated renin of the renal origin and angiotensin converting enzyme in the maintenance of the spontaneous hypertension.

Angiotensin II↗
PubMed1991

Angiotensin converting enzyme inhibitors suppress the vascular renin-angiotensin system of spontaneously hypertensive rats.

The effects of angiotensin converting enzyme (ACE) inhibitors on the release of angiotensin II (Ang II) from isolated mesenteric arteries of spontaneously hypertensive rats (SHRs) were examined. Delapril, enalapril, and captopril suppressed Ang II release in a dose-dependent manner. After oral treatment with delapril (10 mg/kg/day), enalapril (10 mg/kg/day), and captopril (50 mg/kg/day) for 1 week, the blood pressure of SHRs was significantly reduced in the three groups and 54%, 46%, and 36% decreases in basal Ang II release were observed, respectively, compared with control. However, low-dose captopril (10 mg/kg/day) had no effect on blood pressure or basal Ang II release. These results provide clear evidence that ACE inhibitors suppress vascular renin-angiotensin activity of SHRs, and the possible contribution of the tissue renin-angiotensin system to spontaneous hypertension is suggested.

Angiotensin II↗