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S Osumi

Publications and source records attributed to S Osumi.

At least 19 recordsLinked to original sources
PubMed2001

Prostaglandin E(2) (EP(1)) receptor agonist-induced DNA synthesis and proliferation in primary cultures of adult rat hepatocytes: the involvement of TGF-alpha.

We investigated the effects of prostaglandin (EP) receptor subtype agonists on DNA synthesis and proliferation in primary cultures of adult rat hepatocytes to elucidate their mechanisms of action. Maintained in short-term cultures (i.e. 3.5 h) in a serum-free, defined medium, hepatocyte parenchymal cells underwent DNA synthesis and proliferation in the presence of sulprostone (10(-6) M), PGE(2) (10(-6) M), and 17-phenyl-trinor-PGE(2) (10(-9) M) in a time- and dose-dependent manner. PGE(2) was less potent than 17-phenyl-trinor-PGE(2) in stimulating hepatocyte mitogenesis. Sulprostone (10(-6) M) and 11-deoxy-PGE(1) (10(-6) M) showed weak and insignificant stimulation, respectively, for hepatocyte mitogenesis. These effects of PGE(2), 17-phenyl-trinor-PGE(2), and sulprostone were abolished by treatment with a specific EP(1) receptor antagonist, SC-51322, or the PLC inhibitor U-73122. The effects of these EP(1) receptor agonists were potentiated by ionomycin and blocked by verapamil. Hepatocyte mitogenesis was almost completely blocked by specific inhibitors of growth-related signal transducers, such as genistein, wortmannin, PD98059, and rapamycin. A monoclonal antibody against TGF-alpha dose-dependently inhibited PGE(2)- and 17-phenyl-trinor-PGE(2)-induced hepatocyte mitogenesis. Treatment with the EP(1) receptor agonists significantly increased the secretion of TGF-alpha, reaching a maximum within 5 min. The increase in TGF-alpha secretion was blocked by SC-51322, U-73122, somatostatin, and verapamil and potentiated by ionomycin. These results indicate that the proliferative mechanisms of action of EP(1) receptor agonists are mediated through an increase in the autocrine secretion of TGF-alpha, which is dependent on the EP(1) receptor/G-protein involved in PLC regulation/PLC/Ca(2+) system. The locally secreted TGF-alpha, in turn, acts as a complete mitogen that stimulates the tyrosine kinase/MAPK pathway in these cells.

Animals↗
PubMed2000

Stimulation of DNA synthesis and proliferation by prostaglandins in primary cultures of adult rat hepatocytes.

We studied the effects of several prostaglandins on DNA synthesis and proliferation in serum-free primary cultures of adult rat hepatocytes. Maintained in short-term cultures (i.e., 3.5 h), the hepatocyte parenchymal cells synthesized DNA and proliferated in the presence of various prostaglandins in a dose-dependent manner. The half-maximal effective concentrations (ED(50)) of prostaglandin F(2alpha), prostaglandin E(1), prostaglandin E(2) and prostaglandin I(2) for proliferation were estimated to be 1.7 x 10(-9), 2.3 x 10(-8), 2.7 x 10(-8) and 3.3 x 10(-9) M, respectively. Prostaglandin E(2) and prostaglandin I(2) produced greater maximal responses than did either prostaglandin E(1) or prostaglandin F(2alpha). The cells responded only weakly to prostaglandin D(2). The stimulatory effects of 10(-6) M prostaglandin E(1) and 10(-6) M prostaglandin E(2) on hepatocyte DNA synthesis and proliferation were inhibited by a specific antagonist of the EP(1) receptor, 8-chlorodibenz[b, f][1, 4]oxazepine-10(11H)carboxylic acid, 2-[3-[(2-furanylmethyl)-thio]-1-oxopropyl]hydrazide (SC-51322; 10(-6) M). Specific inhibitors of signal transducing elements (e.g., 1-[6-[17beta-3-methoxyestra-1, 3, 5(10)-trien-17-yl]amino] hexyl]-1H-pyrrol-2,5-dione (U-73122); 10(-6) M), 10(-6) M verapamil, 5 x 10(-6) M genistein) almost completely blocked the growth-promoting effects of the prostaglandins. These results suggest that prostaglandins stimulate hepatocyte DNA synthesis and proliferation by their own receptors and exert their effects through both phospholipase C/Ca(2+) and receptor tyrosine kinase pathways.

Animals↗
PubMed1991

Endothelial cells modulate the vasoinhibitory effect of NKY-722, a Ca2+ channel antagonist, in canine mesenteric arteries.

Modulation of the vasoinhibitory effect of NKY-722 by vascular endothelial cells was studied in canine mesenteric arteries. A high concentration of NKY-722 accumulated in the endothelium-intact arteries and its accumulation in endothelium-removed arteries was significantly less. The vasoinhibitory effect of NKY-722 in endothelium-intact arteries was significantly weaker than that in endothelium-removed arteries. These results suggest that endothelial cells can attenuate the vasoinhibitory effect of NKY-722.

Animals↗
PubMed1991

Effect of indapamide on the proliferation of Balb/C 3T3 cells induced by platelet-derived growth factor.

The effects of indapamide (a nonthiazide antihypertensive diuretic) on the growth promoting activity of serum, platelet-derived growth factor (PDGF), fibroblast growth factor (FGF) or Ca3(PO4)2 on Balb/C 3T3 cells were studied. Indapamide inhibited the growth promoting activity of serum, but furosemide (a nonthiazide antihypertensive diuretic) had no such inhibitory effect. Indapamide inhibited the growth promoting activity of PDGF, but not that of FGF and Ca3(PO4)2. The present experiments demonstrate that indapamide selectively inhibits the growth promoting activity of PDGF.

3T3 Cells↗
PubMed1991

Effect of accumulation of NKY-722, a water-soluble vasoselective Ca++ antagonist, on KCl-induced contraction in isolated canine mesenteric arteries.

The relationship between the accumulation of NKY-722 and its vasoinhibitory effect on KCl-induced contraction was examined in canine mesenteric arteries. NKY-722 showed a high level of accumulation in canine mesenteric arteries and reached near maximal levels at 60 min. The tissue/medium ratio measured at 60 min was independent of the bath concentration of NKY-722 (10(-9), 10(-8) and 10(-7) M). NKY-722 (10(-9) and 10(-7) M) attenuated the KCl (30 mM)-induced contraction of canine mesenteric arteries, and this effect was dependent on the pretreatment time (5-60 min). The vasoinhibitory effect of NKY-722 (during incubation) on KCl-induced contraction correlated with its accumulation in the vascular preparations. Preparations were incubated with NKY-722 (5 x 10(-9) M) for 60 min and repetitively washed out, showing that the accumulation of NKY-722 decreased slowly over 300 min. When the preparations were incubated with NKY-722 (5 x 10(-9) M) for 60 min, the vasoinhibitory effect on KCl-induced contraction remained for over 300 min after repetitive washouts. The vasoinhibitory effect of NKY-722 (during washout) on KCl-induced contraction also correlated with its accumulation in the vascular preparations. The present experiments indicate that NKY-722 accumulates in canine mesenteric arteries at high levels and should be washed out slowly, and suggest that NKY-722 accumulation in vessel walls may contribute to the long duration of its antihypertensive effect.

Animals↗
PubMed1990

Radical scavengers of indapamide in prostacyclin synthesis in rat smooth muscle cell.

Indapamide, a nonthiazide diuretic, exhibits direct vasodilator action as well as natriuretic and diuretic effects. Although calcium antagonist-like activity has been addressed so far, the mechanisms for vasodilator effect are still uncertain. To understand the wide range of indapamide actions, we examined the effects of indapamide on the vascular eicosanoid generation and investigated its mechanisms by using rat vascular smooth muscle cells in culture. Indapamide uniquely increased the prostacyclin generation in the vascular smooth muscle cells in a dose-dependent manner, whereas it did not affect the vasoconstrictor thromboxane A2. Thiazide diuretics lowered the prostacyclin generation, while nonthiazide derivatives did not affect the biosynthesis. Enzymatic analysis revealed that indapamide affected neither [14C]arachidonate liberation nor prostacyclin synthase of the smooth muscle cells. Indapamide eliminated a stable free radical in a cell-free system, lowered the formation of malondialdehyde from lipid peroxides in rat brain homogenate, and reduced lipid peroxidation by the free radical generating system of xanthine-xanthine oxidase. Indeed, the scavenging action of indapamide significantly attenuated the inhibitory activity of 15-hydroperoxy-arachidonate to prostacyclin synthase activity. These results indicate that indapamide diuretic increases prostacyclin generation in the vascular smooth muscle cells possibly through antioxidant effects and that the enhanced prostacyclin generation is partly responsible for its direct vasodilator action.

Animals↗
PubMed1988

Inhibitory effects of trimetazidine dihydrochloride on aggregation, serotonin release and malondialdehyde production in rabbit platelets.

Aggregation, serotonin release and malondialdehyde (MDA) production via cyclooxygenase and thromboxane A2 synthetase were investigated in rabbit platelets. Trimetazidine dihydrochloride (TMZ) attenuated the collagen-induced aggregation more strongly than the arachidonic acid (AA)-, thromboxane A2 agonist (U-46619)-, Ca2+-ionophore (A-23187)- and ADP-induced aggregation: IC50 values were 1.0 +/- 0.1, 4.4 +/- 0.3, 4.3 +/- 0.4, 4.1 +/- 0.7 and 3.3 +/- 0.2 mM, respectively. TMZ decreased dose-dependently the serotonin release induced by collagen and A-23187, but did not decrease that induced by AA. TMZ also decreased the MDA production induced by collagen and A-23187 (IC50: 0.3 +/- 0.03 and 1.0 +/- 0.1 mM, respectively), but did not decrease the production induced by AA. Furthermore, TMZ decreased dose-dependently the MDA production induced by exogenous phospholipase A2. On the other hand, indomethacin (10 microM) attenuated the aggregation induced by collagen and AA, but not by the other agents, and decreased the serotonin release and the MDA production induced by collagen, A-23187 and AA. The present results suggest that TMZ may inhibit the process preceding the cyclooxygenase pathway in the AA cascade, and subsequently may attenuate the aggregation and the serotonin release via thromboxane A2 production from endogenous AA.

Animals↗
PubMed1988

Antihypertensive effect of NKY-722, a new water-soluble 1,4-dihydropyridine derivative, on conscious spontaneously hypertensive rats.

3-(4-Allyl-1-piperazinyl)-2,2-dimethylpropyl methyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine dicarboxylate dihydrochloride (NKY-722) produced a dose-dependent antihypertensive effect in conscious spontaneously hypertensive rats (SHR). In this respect NKY-722 was more potent and longer-acting than nicardipine. In canine isolated mesenteric arteries, exposed to a Ca2+-free medium containing high K+, NKY-722 inhibited Ca2+-induced contraction in concentration-dependent manner, suggesting the calcium antagonism as the mechanism of action.

Animals↗
PubMed1982

Influence of trimetazidine, an antianginal drug, on isolated dog arteries and veins.

In helical strips of dog coronary, mesenteric, renal, femoral and basilar arteries contracted with prostaglandin F2 alpha, trimetazidine produced a dose-related relaxation, which was not influenced by treatment with propranolol, atropine, cimetidine, aminophylline and aspirin. Relaxations induced by trimetazidine of strips of large and small coronary arteries did not differ, while those of large artery strips induced by nitroglycerin were significantly greater. Mesenteric vein strips responded with a greater relaxation to trimetazidine than mesenteric artery strips, while the vein and artery strips relaxed in response to nitroglycerin to a similar extent. Contractile responses to transmural stimulation and norepinephrine of mesenteric vein strips were attenuated by trimetazidine to a greater extent than those of artery strips. However, trimetazidine did not protect alpha-adrenoceptors from persistent blockade by phenoxybenzamine. Treatment with high concentrations of trimetazidine attenuated the relaxant response to isoproterenol of coronary arteries and the contractile response to Ca++ of the arteries exposed to Ca++-free media and depolarized by excess K+. It may be concluded that trimetazidine preferentially relaxes venous muscle and reduces contractile responses of veins to activation of sympathetic nerves, thereby reducing venous return or preload of the heart.

Animals↗
PubMed1982

[Antihypertensive and diuretic effects of indapamide in normotensive and hypertensive rats (author's transl)].

Antihypertensive and diuretic actions of indapamide (SE-1520) were investigated in rats and compared with those of trichlormethiazide (TCMT). In normotensive rats, indapamide in a dose of 100 mg/kg p.o. did not show a significant effect on the blood pressure. In DOCA-saline and uni-nephrectomized DOCA-saline hypertensive rats, indapamide above 1 mg/kg and TCMT above 3 mg/kg with single oral or repetitive administration for 2 weeks reduced the blood pressure level. In spontaneously hypertensive rats (SHR), both indapamide and TCMT lowered the blood pressure with single doses above 10 mg/kg or repetitive doses above 3 and 10 mg/kg, respectively. In the diuretic test using normal rats, indapamide in doses ranging from 0.1 to 30 mg/kg increased urine volume and urinary electrolyte excretion. TCMT showed a more potent diuretic action at a lower dose level. In SHR, indapamide and TCMT produced a greater urine volume and electrolytes excretion. Indapamide inhibited the carbonic anhydrase activity and the potency was about 1/25 of that of acetazolamide in vitro. The antihypertensive activity of indapamide was more potent than that of TCMT and the reverse order to that of their diuretic potencies. It is suggested that the mechanism of antihypertensive effect of indapamide is different from that of TCMT.

Animals↗
PubMed1978

[Influence of indapamide on isolated rabbit arteries (author's transl)].

The effect of indapamide, a high ceiling diuretic, antihypertensive drug, was investigated in helically-cut strips of rabbit cerebral, coronary, renal, mesenteric and femoral arteries and aortae. The addition of indapamide in concentrations higher than 3 X 10(-5)M relaxed those arterial strips contracted with prostaglandin F2alpha; the relaxation being greater in cerebral, coronary and renal arteries. Atropine propranolol and aminophylline did not reduce the relaxing effect. Hydrochlorothiazide produced fewer incidences of relaxation. Treatment for 20 min with indapamide (3 X 10(-5) or higher) significantly attenuated the contractile response of mesentric arteries to nicotine and tyramine. Contractile responses to transmural electrical stimulation were not reduced but rather potentiated. The dose-response curve of norepinephrine was not significantly affected by indapamide. The contractile response of nictitating membranes of anesthetized cats to stimulation of preganglionic sympathetic nerves was not influenced by indapamide but was abolished by hexamethonium. It may be concluded that arterial relaxations induced by indapamide are due to a direct action on smooth muscles. Indapamide appears to attenuate the response to nicotine and tyramine by interfering with the mechanism of neuronal amine uptake. However, such does not involve a ganglionic blockade nor a reduction of the release of norepinephrine from adrenergic nerve terminals.

Animals↗