Biomedical subjects

T Inagami

Publications and source records attributed to T Inagami.

At least 271 records · Page 15Linked to original sources

PubMed1988

Norepinephrine and epinephrine in human erythrocyte plasma membranes.

Acetone extract prepared from the plasma membranes of human erythrocytes contained substances which induced the contraction of the thoracic aortic strip of rabbit in vitro and caused blood pressure elevation in rat upon intravenous injection. The contractile response was inhibited by the alpha 1-adrenergic antagonist prazosin. By HPLC/electrochemical detection as well as radioenzymatic assay, large amounts of norepinephrine (NE) (14 +/- 4 [SE] ng/ml packed cells) and epinephrine (E) (16 +/- 2 ng/ml packed cells) were found in the extract. Using the same amounts as in the extract, we were able to demonstrate additive effect between NE and E. The possibility that erythrocyte membranes may play a role in the regulation of NE and E in circulation is suggested.

Angiotensin I↗

PubMed1988

Atrioactivase, a specific peptidase in bovine atria for the processing of pro-atrial natriuretic factor. Purification and characterization.

A seryl protease which catalyzes conversion of proatrial natriuretic factor (ANF) to the active circulating form, ANF(99-126), was purified from a particulate fraction of bovine atria. The enzyme was solubilized with 1.6 M KCl. The molecular mass of the purified enzyme was 580 kDa on gel filtration, whereas by sodium dodecyl sulfate-polyacrylamide gel electrophoresis a cluster of six bands with molecular masses around 30 kDa was observed. The purified enzyme produced ANF(99-126) from partially purified bovine pro-ANF by the selective cleavage of the arginyl peptide bond in the -Pro97-Arg98-Ser99-sequence in pro-ANF. The enzyme was localized mainly in the microsomal fraction rather than the granule fraction. It is likely that the enzyme selectively cleaves the Arg98-Ser99 peptide bond in pro-ANF during the process of secretion.

Animals↗

PubMed1988

Isolation and characterization of a specific endogenous Na+,K+-ATPase inhibitor from bovine adrenal.

In order to identify a specific endogenous Na+,K+-ATPase inhibitor which could possibly be related to salt-dependent hypertension, we looked for substances in the methanol extract of bovine whole adrenal which show all of the following properties: (i) inhibitory activity for Na+,K+-ATPase; (ii) competitive displacing activity against [3H]ouabain binding to the enzyme; (iii) inhibitory activity for 86Rb uptake into intact human erythrocytes; and (iv) cross-reactivity with sheep anti-digoxin-specific antibody. After stepwise fractionation of the methanol extract of bovine adrenal glands by chromatography on a C18 open column, a 0-15% acetonitrile fraction was fractionated by high-performance liquid chromatography on a Zorbax octadecylsilane column. One of the most active fractions in 0-15% acetonitrile was found to exhibit all of the four types of the activities. It was soluble in water and was distinct from various substances which have been known to inhibit Na+,K+-ATPase such as unsaturated free fatty acids, lysophosphatidylcholines, vanadate, dihydroxyeicosatrienoic acid, dehydroepiandrosterone sulfate, dopamine, lignan, ascorbic acid, etc. This substance was further purified by using an additional five steps of high-performance liquid chromatography with five different types of columns. Molecular mass was estimated as below 350 by fast atom bombardment mass spectroscopy and ultrafiltration. Heat treatment at 250 degrees C for 2 h and acid treatment with 6 N HCl at 115 degrees C for 21 h almost completely destroyed the inhibitory activity of the purified substance for Na+ pump activity. Additionally, alkaline treatment with 0.2 N NaOH at 23 degrees C for 2 h destroyed approximately 70% of the inhibitory activity, whereas boiling for 10 min and various enzyme digestion did not destroy the activity. The dose dependency for the four types of the activities for this substance paralleled those of ouabain, spanning 2 orders of magnitude in concentration range. The inhibitory potencies of the purified substance for Na+,K+-ATPase, Na+ pump, and ouabain binding activities were diminished with increasing K+ concentration, exhibiting a characteristic typical of cardiac glycosides. This substance had no effect on the Ca2+-ATPase activity or the Ca2+ loading rate into the vesicle prepared from skeletal muscle sarcoplasmic reticulum. These results strongly suggest that this water-soluble nonpeptidic Na+,K+-ATPase inhibitor may be a specific endogenous regulator for the ATPase.

Adenosine Triphosphatases↗

PubMed1988

Immunohistochemical renin study of DES-induced renal tumor in the Syrian hamster.

Diethylstilbestrol (DES) treatment of a male Syrian hamster resulted in the development of a renal tumor and its widely scattered serosal metastases. Cells in both the primary tumor and metastatic nodules contained secretory granules. The tumors were transplanted serially into DES-supported and non-DES-supported host hamsters until DES-independent tumors developed. Rabbit antiserum to mouse salivary renin and rabbit antiserum to rat kidney resin were reacted with sections of the primary tumor, metastatic nodules, and all transport tumors. The sections were stained by the PAP and Vector-ABC-AP procedures. Renin-positive material was observed in all tumors. Plasma renin activity (PRA) was determined for the host hamsters carrying the renal tumor transplants and compared to the PRA values that had been determined for normal non-DES-treated male and female hamsters. It was found that the average PRA values of host hamsters carrying the tumor transplants were significantly higher than the normal PRA values.

Animals↗

PubMed1988

The renin-angiotensin system: an overview of its intracellular function.

The enzyme renin has been purified and characterized by structural analysis. Pure renin protein was used to produce a specific antibody to renin, which was useful in demonstrating the presence of a specific renin in many tissues other than kidney. Further, in these cells angiotensins I and II and converting enzyme all were found to coexist with renin by immunohistochemical studies, indicating the local production of renin, angiotensinogen and angiotensins in these cells. Angiotensin II produced in the cultured cells was secreted to the outside of the cells. Secretion of angiotensin II from the angiotensin-producing cells was demonstrated with perfused mesenteric artery. The secretion of angiotensin II from the vascular beds was inhibited by converting enzyme inhibitors, and was stimulated by the adrenergic beta-agonist isoproterenol. These studies demonstrate local production and controlled secretion of angiotensin II and define its physiologic role.

Angiotensin II↗

PubMed1988

Effect of vasodilator prostaglandins on the vascular renin-angiotensin system.

The interaction of prostaglandin (PG) with the vascular renin-angiotensin (R-A) system was examined by studies on the effects of PGI2, PGE2 and the inhibitor of PG synthesis, indomethacin, on the release of angiotensin II (Ang II) from isolated rat mesenteric arteries. The Ang II released from the vasculature was measured after its concentration in a Sep-Pak C18 cartridge connected to the perfusion system. After perfusion with drugs, the specific vascular renin activity inhibited by anti-renin antibody was determined. The basal perfusion pressure was constant (19.6 +/- 1.1 mmHg) at a flow rate of 4.5 ml/min, and was not changed by any of these drugs. The basal levels of Ang II release and vascular renin activity were 44 +/- 5 pg/30 min and 113 +/- 8 pg Ang I/mg protein/hr, respectively. Infusion of PGI2 (10(-6) M) significantly decreased both Ang II release (p less than 0.01) and vascular renin activity (p less than 0.05) as compared with the control levels. Infusion of PGE2 (10(-6) M) decreased Ang II release significantly (p less than 0.05) and vascular renin activity slightly. Infusion of indomethacin (10(-6)M) increased vascular renin activity significantly (p less than 0.01). Pretreatment with indomethacin (10 mg/kg, ip) for 2 days also increased vascular renin activity (p less than 0.01). These results indicate that in contrast to their effects on the renal R-A system, PGs suppress the vascular R-A system and that these two local vasoactive factors interact to regulate vascular tone.

Angiotensin II↗

PubMed1988

Effect of sodium ion on atrial natriuretic factor release from rat hypothalamic fragments.

The effects of Na ion and choline chloride on the release of atrial natriuretic factor (ANF) and growth hormone-releasing factor (GHRF) from rat hypothalamic fragments including the organum vasculosum of the lamina terminalis (OVLT) were examined in vitro. Although the release of ANF was stimulated by Na ion, choline chloride, and glucose in concentration-dependent manners, the release was more sensitive to a change in concentration of Na ion than to those of choline chloride and glucose. On the other hand, the change in Na ion concentration did not affect the release of GHRF. It can be therefore proposed that Na ion is the first candidate controlling ANF release from the brain tissue and that ANF in the hypothalamus and/or OVLT may play some role in the regulation of the Na ion and water balance in the central nervous system.

Animals↗

PubMed1988

Plasma human atrial natriuretic factor in cirrhosis and ascites with and without functional renal failure.

Functional renal failure of cirrhosis (FRFC) is a usually fatal syndrome of acute renal failure occurring in patients with advanced liver disease. Although not conclusively proven, most evidence suggests that renal arterial and arteriolar vasoconstriction is the cause of the renal failure in these patients. However, the mediators of the vasoconstriction remain unknown. Human atrial natriuretic factor (hANF) is a hormone with potent natriuretic, diuretic, and vasorelaxant properties. A deficiency of hANF could lead to renal arterial vasoconstriction and avid renal sodium retention as seen in FRFC. This study was undertaken to determine if patients with FRFC are deficient in circulating hANF. Seven patients with advanced alcoholic liver disease and renal failure of unknown cause (FRFC) were compared with 7 patients with advanced alcoholic liver disease, ascites, and normal serum creatinine as well as with 14 healthy volunteers. Plasma hANF was measured by radioimmunoassay. Plasma hANF was 742 +/- 227 pg/ml (mean +/- SEM) in patients with FRFC compared with 360 +/- 70 pg/ml in patients with liver disease and normal serum creatinine (p greater than 0.05) and 28 +/- 5.7 pg/ml in healthy volunteers (p less than 0.005 vs. FRFC and chronic liver disease, ascites, and normal serum creatinine). Thus, FRFC is not caused by a deficiency of circulating hANF. The elevated plasma hANF levels in patients with chronic liver disease and continued sodium retention may suggest a renal insensitivity to the natriuretic effects of hANF.

Adult↗

PubMed1988

Immunohistochemical localization of renin in end-stage kidneys.

Hypertension in chronic renal failure is usually due to excessive accumulation of salt and water. In some cases, sodium and volume depletion by dialysis fail to reduce the high BP, and plasma renin activity tends to be higher. We performed a semiquantitative analysis of the immunohistochemical distribution of renin in the kidneys of ten patients with end-stage renal disease and hypertension using a specific antihuman renin antibody and a peroxidase-antiperoxidase technique on paraffin sections of nephrectomy and/or autopsy specimens. In five cases with severe, dialysis-resistant hypertension, the degree of immunoreactivity was most striking, exceeding that found in renovascular hypertension and present in arterioles at a distance from the glomeruli. Three cases of advanced diabetic glomerulosclerosis consistently showed minimal immunoreactivity. We conclude that renin often can be detected immunologically in the kidney of patients with chronic renal failure and hypertension, but its pathophysiological role will require further study.

Adolescent↗

PubMed1988

Conceptual evolution of renin research.

Research on renin in the last 90 years has undergone numerous conceptual evolution since its discovery by Tigerstedt and Bergman in 1898. This paper briefly reviews the evolutionary steps leading up to the recently discovered intracellular function of renin and generation of angiotensin II in renin containing cells and molecular biological studies approaching the regulation of renin expression in various tissues.

Animals↗

PubMed1988

Renin in glioblastoma multiforme and its role in neovascularization.

Significant proliferation of capillaries with hyperplastic vascular endothelium is one of the characteristic histologic features of glioblastoma multiforme (GBM). It has been shown that the renin-angiotensin II cascade stimulates new vessel formation. The presence of renin in several types of highly vascularized neoplasm suggests that it may also be implicated in the mechanism of tumor angiogenesis. In order to study the possible relationship of renin to GBM, immunohistochemical search for human renin was carried out in ten instances of such a tumor. Eight of these cases demonstrated renin-containing neoplastic astrocytes, whereas seven cases of reactive gliosis and six cases of low-grade astrocytoma revealed no renin-containing cells. The immunostaining was not present after preabsorption of the renin antiserum with pure human renin or substitution of preimmune serum for the specific renin antiserum. Because it has also been demonstrated that a product of renin, angiotensin II, has angiogenic properties, it seems reasonable to postulate that renin, through angiotensin II, may play a role in the mechanism of GBM-associated neovascularization.

Brain↗

PubMed1988

Purification and characterization of specific endogenous ouabainlike substance from bovine adrenal.

Endogenous inhibitors of Na, K-ATPase have been implicated in the pathogenesis of salt-induced hypertension. Despite an intensive search, the inhibitor(s) have long remained elusive. We have been able to purify such an inhibitor from methanol extracts of bovine adrenal glands by multiple steps of high-performance liquid chromatography (HPLC). This compound showed striking similarity to the cardiac glycoside ouabain in its dose dependency in the inhibition of Na, K-ATPase and Na-pump activity, competitive binding to the ouabain-binding site, and dependence of these effects on K+ concentration. These results indicate that vertebrate animals contain a regulator of Na, K-ATPase.

Adrenal Glands↗

PubMed1988

Kidney tubular epithelium cells and vascular smooth muscle cells contain different types of atrial natriuretic factor receptors.

We have identified and characterized three distinct atrial natriuretic factor (ANF) receptor subtypes from cultured canine kidney tubular (MDCK) cells and rat thoracic aortic smooth muscle cells. These are (1) a disulphide-linked 140-kDa protein found in rat thoracic aortic smooth muscle cells which was reduced by dithiothreitol to a 70-kDa band, (2) a disulphide-unlinked 120-kDa protein, specific to canine kidney tubular cells, whose molecular weight was not reduced by dithiothreitol and (3) a 66-70 kDa protein prevalent in both types of cell whose molecular weight was not reduced by dithiothreitol. The non-reducible 66-70 kDa and the reducible 140 kDa proteins showed strong affinities to the full-length ANF-(99-126) and truncated ANF-(103-123); however, the non-reducible 120-kDa protein showed strong affinity only to ANF-(99-126). Both ANF-(99-126) and ANF-(103-123) stimulated cyclic (c)GMP in the rat smooth muscle cells but only ANF-(99-126) stimulated cGMP in the canine tubular cells. Distinct ANF receptor subtypes might be linked to diverse physiological functions of ANF such as natriuresis and diuresis in kidney and vasorelaxation in vascular smooth muscle cells.

Affinity Labels↗

PubMed1988

Immunoreactive prorenin and its profragment peptide are present in human juxtaglomerular cells.

Although prorenin appears to be activated through the cleavage of its prosegment in the juxtaglomerular cells, the presence of prosegment peptide has never been demonstrated. We therefore studied prorenin in juxtaglomerular tumour cells, both by immunohistochemistry and by radio-immunoassay. Synthetic peptide covering the 14-carboxyterminal sequence of human renin prosegment was used to prepare both antibody and radiolabelled tracer. Intense immunostaining of prorenin was demonstrated in the tumour cells. By gel filtration, however, immunoreactive prorenin was shown to consist of two major components. The first peak, located at the elution position of activatable inactive renin, was regarded as prorenin. The other peak was located at an elution position with a smaller molecular weight, which was assumed to represent the profragment. These results suggest that both prosegment peptide and prorenin are present in the juxtaglomerular cells.

Adult↗

PubMed1988

Interaction between the vascular renin-angiotensin system and prostaglandins.

The effects of nephrectomy, prostacyclin (PGI2), prostaglandin E2 (PGE2) and indomethacin on the vascular renin-angiotensin system were examined using isolated perfused mesenteric arteries. Angiotensin II (Ang II) released from the vasculature was measured using a Sep-Pak C18 cartridge which was placed in the perfusion system. After perfusion with drugs, the specific vascular renin activity inhibited by antirenin antibody was determined. Plasma renin activity was markedly decreased 48 h after nephrectomy, whereas vascular renin activity was increased. Released Ang II from mesenteric arteries of nephrectomized rats was not significantly different from that in control rats. Infusion of PGI2 (10(-6) mol/l) and PGE2 (10(-6) mol/l) for 1 h caused significant decreases in Ang II release (P less than 0.01 and P less than 0.05, respectively) and also decreased vascular renin activity. In contrast, infusion of indomethacin (10(-6) mol/l) for 1 h resulted in an increase (P less than 0.01) in vascular renin activity. These findings suggest that the vascular renin-angiotensin system exists independently of the circulating renin-angiotensin system. In contrast with their effects on renal renin, prostaglandins suppress the vascular renin-angiotensin system. The interaction between two vasoactive hormones in the vascular wall may be important for local regulation of vascular tone and regional blood flow.

Angiotensin II↗

PubMed1988

Direct evidence for the local generation of vascular angiotensin II and its prostaglandin-mediated release from isolated hind legs in the rat.

We examined the effect of prostaglandin synthesis inhibitors (indomethacin and meclofenamate) on the release of immunoreactive angiotensins I (irAng I) and II (irAng II) from isolated perfused rat hind-leg vasculature in order to delineate the possible relevance of prostaglandins to the vascular renin-angiotensin system in vitro. Isolated rat hind-legs were perfused with Krebs-Ringer solution and release of irAng I and irAng II into the perfusate was directly measured by using a Sep-Pak C18 cartridge connected to the perfusion system. The spontaneous release of irAng I and irAng II was as high as 600-700 pg per 30 min and was stable for at least 3 h. Addition of indomethacin and meclofenamate (10(-8) to 2 X 10(-6) mol/l) to the perfusion medium suppressed the release of both irAng I and irAng II to a similar extent in a dose-dependent fashion (P less than 0.001); the maximal percentage inhibition of irAng II release that was evoked by these inhibitors (2 X 10(-6) mol) was 60 +/- 6% (P less than 0.001) for indomethacin and 50 +/- 4% (P less than 0.001) for meclofenamate. There was a highly significant positive correlation between the amount of irAng I released and the amount of irAng II that was altered by indomethacin (r = 0.91) or meclofenamate (r = 0.94). These results provide direct proof of the local generation and subsequent release of Ang II by peripheral vascular tissue and suggest that prostaglandin plays an important role in the regulation of vascular Ang II release.

Angiotensin I↗

PubMed1988

Localization and secretion of newly synthesized and stored renin: two compartments and secretory mechanisms.

Intracellular pathways of renin secretion were examined by use of rat renal cortical slices. Renin was labeled with [35S]methionine by incubating the cortical slices for 2 h. The labeled immunoprecipitable renin was found in microsomal fraction (F1) but not in the renin granule fraction (F2). The newly synthesized and radiolabeled renin was secreted from the incubated slices into the medium. The rate of secretion of the labeled renin activity was not increased by 10(-6) M isoproterenol, whereas secretion of total renin activity was markedly stimulated. The isoelectric focusing patterns of renin in F1 and F2 were compared with those secreted with or without isoproterenol. The pattern of F1 was similar to that secreted in the medium without stimulation. These studies suggest that a constitutive pathway exists for renin secretion from the kidney and that the constitutive (nonstimulable) pathway is responsible for the secretion of newly synthesized renin and that it is not stimulated by a beta-adrenergic mechanism.

Animals↗

PubMed1988

Local generation and release of angiotensin II in peripheral vascular tissue.

Isolated rat hindlegs were perfused with Krebs-Ringer solution, and immunoreactive angiotensin II (irAng II) released into the perfusate was directly determined using a Sep-Pak C18 cartridge connected to the perfusion system. High performance liquid chromatography clearly demonstrated the presence of angiotensin I (Ang I), angiotensin II (Ang II), and a small amount of angiotensin III. The spontaneous release of irAng II was as high as about 600 pg/30 min, which was stable up to 3 hours. Captopril added to the perfusion medium (10(-9) to 10(-6) M) suppressed irAng II release in a dose-dependent manner (p less than 0.001), and it (10(-6)M) caused a reciprocal increase of irAng I release (p less than 0.05). Oral pretreatment of captopril (50 mg/kg/day) for 1 week suppressed the irAng II release by 31% (p less than 0.02). The same treatment with SA 446, a highly lipophilic angiotensin converting enzyme inhibitor, inhibited the irAng II release by 63% (p less than 0.001). On the other hand, the two inhibitors suppressed the plasma irAng II to very similar extents. Pretreatment with SA 446 plus nephrectomy did not cause any further change in irAng II release as compared with that with SA 446 alone. These results provide direct proof for local generation and subsequent secretion of Ang II by peripheral vascular tissue.

3-Mercaptopropionic Acid↗