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T Saruta

Publications and source records attributed to T Saruta.

At least 253 records · Page 14Linked to original sources
PubMed1995

Pressure enhances endothelin-1 release from cultured human endothelial cells.

The effect of pure pressure without shear stress or stretch on the release of endothelin-1 was investigated. Elevation of pressure significantly enhanced endothelin-1 release from cultured human umbilical vein endothelial cells. A calcium channel blocker, nifedipine, and a putative stretch-activated channel blocker, gadolinium, did not affect the pressure-induced endothelin-1 increase. On the other hand, a phospholipase C inhibitor, 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate, and protein kinase C inhibitors, 1-5-(isoquinolinylsulfonyl)-2-methylpiperazine and chelerythrine, significantly inhibited the pressure-induced endothelin-1 increase. Moreover, pure pressure reduced basal nitric oxide release, while pretreatment with a nitric oxide synthase inhibitor, NG-monomethyl-L-arginine, had no effect on the pressure-induced endothelin-1 increase. In conclusion, our results show for the first time that pressure enhances endothelin-1 release partially through activation of phospholipase C and protein kinase.

Calcium Channels↗
PubMed1995

Cyclosporin A inhibits nitric oxide synthase induction in vascular smooth muscle cells.

The effect of cyclosporin A on induction of nitric oxide synthase in rat aortic smooth muscle cells was examined. A combination of interleukin-1 alpha (100 U/mL) and tumor necrosis factor--alpha (5000 U/mL) induced accumulation of nitrite/nitrate, the stable end products of nitric oxide, in culture media within 48 hours. Cyclosporin A inhibited this nitrite/nitrate accumulation in a concentration-dependent manner with an IC50 of 4 x 10(-7) mol/L when applied simultaneously with the cytokines. The expression of inducible nitric oxide synthase messenger RNA (mRNA) induced by the combination of interleukin-1 alpha and tumor necrosis factor-alpha was inhibited by the cyclosporin A cotreatment. Cyclosporin A did not decrease inducible nitric oxide synthase mRNA stability in the presence of transcription inhibitor actinomycin D (5 micrograms/mL). Induction of nitrite/nitrate production by the combination of tumor necrosis factor-alpha and bacterial lipopolysaccharide or that of interleukin-1 alpha and interferon gamma (100 U/mL) was also inhibited by cyclosporin A cotreatment. Another inhibitor of calcineurin, FK506 (up to 10(-6) mol/L), had no effect on the induction of nitrite/nitrate production, suggesting the possibility that the inhibitory effect of cyclosporin A may be exerted by means of a novel pathway other than inhibition of calcineurin. These results indicate that cyclosporin A inhibits inducible nitric oxide synthase induction at the mRNA level and that inducible nitric oxide synthase in vascular smooth muscle cells can be a target for cyclosporin A, providing a possible mechanism for the interference of the drug with the balance of vasoactive substances.

Amino Acid Oxidoreductases↗
PubMed1995

Nitric oxide modulates but does not impair myogenic vasoconstriction of the afferent arteriole in spontaneously hypertensive rats. Studies in the isolated perfused hydronephrotic kidney.

Renal autoregulation curves are reset toward higher renal arterial pressure in spontaneously hypertensive rats (SHR) compared with those in Wistar-Kyoto rats (WKY). We previously demonstrated that myogenic afferent arteriolar constriction is shifted to higher renal arterial pressure. To investigate whether nitric oxide participates in the regulation of myogenic tone, we examined the effect of nitro-L-arginine on myogenic afferent arteriolar constriction in kidneys from SHR and WKY, using the isolated perfused hydronephrotic kidney. Elevating pressures from 40 to 80 mm Hg caused increases in afferent arteriolar diameter in WKY (from 18.2 +/- 0.4 to 19.0 +/- 0.3 micron) and SHR (from 17.3 +/- 0.6 to 18.4 +/- 0.6 micron). Further pressure elevation elicited constriction at 100 mm Hg in WKY (17.9 +/- 0.3 micron), but significant constriction was observed at 120 mm Hg in SHR (17.3 +/- 0.6 micron), indicating a resetting in myogenic responses to higher pressures. In WKY, after treatment with 10 mumol/L nitro-L-arginine, afferent arterioles exhibited pressure-dependent constriction, with a threshold pressure for constriction at 80 mm Hg. The addition of 100 mumol/L nitro-L-arginine had no further effect on myogenic responsiveness in WKY. In contrast, in SHR, nitro-L-arginine dose-dependently shifted the myogenic responses toward lower renal arterial pressure, with threshold pressures for constriction observed at 100 mm Hg (10 mumol/L) and 80 mm Hg (100 mumol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Differential modulation of baroreceptor sensitivity by long-term antihypertensive treatment.

We investigated the effects of long-term oral treatment with four different classes of antihypertensive drugs (a thiazide diuretic [trichlormethiazide, 10 mg/kg per day]; a beta-blocker [atenolol, 90 mg/kg per day]; a calcium channel antagonist [nicardipine, 150 mg/kg per day]; and an angiotensin-converting enzyme inhibitor [enalapril maleate, 10 mg/kg per day]) on aortic baroreceptor activity in spontaneously hypertensive rats with chronic hypertension (36 weeks of age). Treatment with each of the four drugs, given from 10 to 36 weeks of age, similarly decreased arterial pressure (171 +/- 2 to 144 +/- 1 mm Hg, P < .01) and similarly decreased the threshold pressure for baroreceptors (116 +/- 3 to 103 +/- 1 mm Hg, P < .05). The four antihypertensive drugs also potentiated the maximal gain of the pressure-activity relation in these rats (untreated, 1.08 +/- 0.05% maximum/mm Hg); however, nicardipine and enalapril (1.77 +/- 0.04% and 1.70 +/- 0.06% maximum/mm Hg, respectively) augmented the maximal gain to a greater extent (P < .05 to .01) than did trichlormethiazide or atenolol (1.49 +/- 0.05% and 1.42 +/- 0.02% maximum/mm Hg, respectively). When the initiation of treatment was delayed to 28 weeks of age, no differences were found in the effects on either threshold pressure (104 +/- 1 mm Hg) or maximal gain (1.36 +/- 0.03% maximum/mm Hg) for all four drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1995

Gene expression of angiotensin II receptor in blood cells of Cushing's syndrome.

The relation between serum cortisol, plasma renin activity, angiotensin II (Ang II), or aldosterone levels and peripheral blood cell (mononuclear leukocytes and platelets) angiotensin II type 1A (AT1A) and 1B (AT1B) receptor mRNA levels was examined in both patients with Cushing's syndrome (seven patients with Cushing's syndrome due to unilateral adrenal cortical adenoma) and control subjects (seven normotensive patients with renal cell carcinoma). Blood was collected from each participant for estimation of plasma renin activity and plasma angiotensin II, aldosterone, and cortisol concentrations and for isolation of mononuclear leukocytes and platelets, which were then used to measure AT1A and AT1B receptor mRNA levels before and after adrenalectomy with the use of reverse transcription-polymerase chain reaction. In patients with Cushing's syndrome, both mononuclear leukocyte and platelet AT1A mRNA levels, which were elevated, were reduced after removal of the adrenal tumors, whereas AT1B receptor mRNA levels of both types of blood cells did not significantly change after adrenalectomy. In contrast, in control subjects, both AT1A and AT1B receptor mRNA levels did not significantly change after unilateral adrenalectomy and nephrectomy. In the adrenal tumors of patients with Cushing's syndrome, gene expression of AT1A receptor was decreased compared with that from adrenals of control subjects. AT1A receptors of the platelets were shown to be upregulated in a manner similar to those of mononuclear leukocytes in patients with Cushing's syndrome. These results suggest that cortisol excess is an important factor upregulating AT1A receptor mRNA levels in human blood cells.

Adenoma↗
PubMed1995

Angiotensin II pressor activity depends on medial and lateral anterior hypothalamic pathways.

The preoptic region of hypothalamus was disconnected from caudal structures with two different-size knife cuts in rats to investigate the pathway responsible for the effects of intracerebroventricular (ICV) and intravenous (IV) angiotensin II (ang II) on blood pressure and arginine vasopressin (AVP) release. Seven days after surgery ICV ang II (125 ng) in sham-operated (sham) rats increased mean arterial pressure (MAP) (+23 +/- 3 mmHg) and decreased heart rate (HR) (-58 +/- 5 beats/minute). However, ICV ang II had no effect on MAP or HR of rats with a large (preoptic-hypothalamic disconnection) cut. Both the pressor response (+12 +/- 2 mmHg) and the bradycardia (-39 +/- 6 beats/minute) were significantly reduced by a small (medial preoptic-hypothalamic disconnection) cut. The increased plasma AVP to ICV ang II in sham rats (9.8 +/- 3.6 pg/mL) was abolished in large-cut rats and attenuated in small-cut rats (3.2 +/- 0.7 pg/mL). IV bolus injection of ang II (125 ng) in sham rats increased MAP by 43 mmHg, whereas large-cut rats showed a blunted (25%) pressor response. The pressor response to IV infusion of ang II (8 ng/20 microL/minute for 15 minutes) was diminished in large-cut rats (+4 +/- 1 mmHg) as compared with that in sham rats (+19 +/- 2 mmHg). Both cuts transected the projection between the periventricular tissue surrounding the anteroventral third ventricle and supraoptic nucleus, but the supraoptic-neurohypophyseal pathway was severed only by the large cut.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1995

Natriuretic peptide-augmented induction of nitric oxide synthase through cyclic guanosine 3',5'-monophosphate elevation in vascular smooth muscle cells.

To elucidate the role of natriuretic peptides in vascular remodeling, the effects of atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide (CNP) on the induction of inducible nitric oxide (NO) synthase (iNOS) in rat aortic smooth muscle cells were examined. Although none of the peptides when applied alone induced the production of nitrite, a stable end product of NO, each peptide dramatically enhanced nitrite production induced by a cytokine combination of interleukin-1 alpha and tumor necrosis factor-alpha. Each natriuretic peptide stimulated intracellular cGMP accumulation in a dose-dependent manner. Time-dependent nitrite production by the cytokines was increased by CNP cotreatment and inhibited by NG-methyl-L-arginine, indicating involvement of the L-arginine-NO pathway. Northern blot analysis showed that the augmented nitrite production was accompanied by an increase in iNOS messenger RNA. A cGMP analog, 8-bromo-cGMP, completely mimicked all of the effects of CNP described above. A cGMP-dependent protein kinase inhibitor, KT5823, paradoxically increased nitrite production and iNOS messenger RNA levels induced by the combination of 8-bromo-cGMP and both cytokines or by the two cytokines only. These data demonstrate the stimulatory effect of cGMP on cytokine-induced iNOS and imply that natriuretic peptides may play a regulatory role in vascular remodeling via the production of large amounts of NO.

Amino Acid Oxidoreductases↗
PubMed1995

Nitric oxide is important for mouse beta-cell line killing by peritoneal exudate cells obtained from cyclophosphamide treated non-obese diabetic mice.

Macrophages from recent onset non-obese diabetic (NOD) mice showed cytotoxicity against the NOD mouse derived beta-cell line, MIN6N-9a. In this report, we examined whether nitric oxide is associated with beta-cell destruction. Peritoneal exudate cells (PEC), obtained from cyclophosphamide treated NOD mice showed higher cytotoxicity against MIN6N-9a compared to PECs from saline injected NOD mice (P < 0.01). This effect was suppressed in cells incubated with 0.5 mmol/l NG-methyl-L-arginine, a nitric oxide synthase inhibitor (P < 0.001). In addition, the nitrite concentration of the co-culture medium, as an index of nitric oxide production, increased in MIN6N-9a cells co-cultured with peritoneal exudate cells from cyclophosphamide injected NOD mice but not in co-culture with saline injected NOD mice (P < 0.05). Thus, nitric oxide plays an important role in beta-cell line destruction of macrophages obtained from NOD mice.

Amino Acid Oxidoreductases↗
PubMed1995

Interactions between angiotensin II and norepinephrine on renin release by juxtaglomerular cells.

While the interactions between angiotensin II (Ang II) and norepinephrine (NE) on cardiovascular responses are well known, their effects on renin responses are not. We determined the renin secretion rate (RSR) and intracellular calcium level in juxtaglomerular cells harvested from Sprague-Dawley rats using a radioimmunoassay and a two-dimensional calcium analyzer. The effect of Ang II and NE was inhibitory on RSR and stimulatory on intracellular calcium. The NE-induced RSR response was amplified in the presence of Ang II (20 nmol/l). The NE-induced intracellular calcium response was also potentiated by the Ang II. There was a significant correlation (r = 0.994, p < 0.0001) between the changes in the RSR and those in intracellular calcium levels. Losartan (0.1 mumol/l). an Ang II type 1 receptor antagonist, blocked the Ang II threshold RSR responses and completely abolished the Ang II-related enhancements. The exclusion of calcium from the buffer reduced the maximal RSR response to NE but did not prevent the enhancement, suggesting the importance of the mobilization of intracellular calcium in the mechanism. The Ang II-induced RSR was amplified in the presence of NE (0.2 mumol/l). The Ang II-induced intracellular calcium response was also potentiated by the NE. A significant correlation (r = 0.996, p < 0.0001) between the changes in the RSR and the changes in intracellular calcium levels was also noted. Prazosin (1 mumol/l), an alpha 1-adrenoceptor antagonist, blocked the NE threshold RSR responses and abolished the agonist-related enhancements. The calcium-free buffer diminished this amplication with a slight decrease in the maximum RSR response to Ang II.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1995

Effect of nonpeptide vasopressin receptor antagonists on developing, and established DOCA-salt hypertension in rats.

Efficacy of orally available, selective vasopressin V1 and V2 receptor antagonists on the developing and established stage of DOCA-salt hypertension was investigated. Twenty-nine Wistar rats were heminephrectomized, and administered DOCA (50 mg/kg; intraperitoneally twice a week) and salt (5% NaCl diet) from week 0 to the end of study. Group 1 rats were served as control. Group 2 and 5 rats were given a V1 antagonist, and groups 3 and 6 rats were given a V2 antagonist, while groups 4 and 7 rats received both V1 and V2 antagonists. Each drug was started to groups 2, 3 and 4 at week 0, and to groups 5, 6 and 7 at week 4. Significant amelioration of the increase in blood pressure was observed in groups 3 and 4 at week 10, and a reduction in blood pressure occurred in groups 6 and 7 at week 10. Otherwise, a V1 antagonist alone slightly attenuated blood pressure rise in the group 2 without significance, and failed to lower blood pressure of the group 5 during the study. These results suggest that both V1 and V2 agonisms are involved in an increase in blood pressure at the developing stage of DOCA-salt hypertension, and that V2 agonism, but not V1 plays a major role in the maintenance of high blood pressure at the established stage.

Administration, Oral↗
PubMed1995

Clinical evaluation of bevantolol hydrochloride in patients with severe hypertension. The Cooperative Study Group on Bevantolol in Japan.

The clinical efficacy and safety of bevantolol hydrochloride, a newly developed beta-blocker, used in combination with other types of antihypertensive agents, were evaluated in patients with severe hypertension by multicenter open-label trials. A total of 28 patients were studied at 20 medical centers. Four patients (14.3%) were excluded for some reasons, and the remaining 24 patients (22 outpatients and 2 inpatients) were analyzed. Following the initiation of therapy, blood pressure decreased from 181 +/- 15 (SD)/114 +/- 3 mmHg to 170 +/- 17/102 +/- 8 mmHg (p < 0.01) on the 14th day of the therapy and gradually lowered further thereafter. At the end of the trial (8th week), blood pressure was stabilized at the level of 160 +/- 14/96 +/- 10 mmHg. The antihypertensive efficacy rated by the changes in mean blood pressure was 79.2% (19/24). Pulse rate decreased slightly but significantly from 75 +/- 10 beats/min to 70 +/- 7 (p < 0.05) on the 14th day of the therapy and stabilized at the similar level thereafter. As abnormal laboratory data were detected in 3 patients and 1 patient complained of a mild headache, the safety ratio was 83.3% (20/24 patients). When the usefulness was assessed in terms of antihypertensive efficacy and safety profiles, bevantolol hydrochloride was considered useful in 75.0% of the patients studied. In conclusion, bevantolol hydrochloride, used in combination with other classes of antihypertensive agents, appears to be an excellent drug for the management of patients with severe hypertension.

Adrenergic beta-Antagonists↗
PubMed1995

Renal effects of amlodipine.

The effects of a new dihydropyridine calcium channel blocker, amlodipine, on blood pressure (BP) and renal function were studied in spontaneously hypertensive rats (SHR). These effects were compared with those of an angiotensin-converting enzyme (ACE) inhibitor, enalapril. In addition, the effects of amlodipine on BP and renal function were studied in hypertensive patients with renal impairment. In five of six nephrectomised salt-loaded SHR, increases in BP, urinary excretion of protein and serum creatinine were attenuated by the administration of 2 mg/kg/day of amlodipine. The progression of renal histological damage was also markedly decreased. The protective effects of amlodipine against renal damage were similar to those of enalapril. However, the mechanisms of action of these two agents seem to differ as, unlike enalapril, amlodipine did not significantly dilate the efferent arteriole in hydronephrotic perfused rat kidney. In a clinical study, 2.5-5 mg/day of amlodipine was administered once a day for 8-10 weeks to 39 hypertensive patients with renal impairment (serum creatinine > or = 1.5 mg/dl to < 5 mg/dl) or renal parenchymal disease (serum creatinine < 5 mg/dl). A significant reduction in BP (reduction of mean BP > or = 13 mm Hg) was observed in 28 patients (80%). Headache was experienced as a side-effect in one of 35 patients (2.9%). With respect to the influence of amlodipine on renal function, mean values of blood urea nitrogen and serum creatinine were unchanged for the total group whereas a slight elevation of serum creatinine was observed in four of 35 patients (11.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Imidapril hydrochloride in essential hypertension: a double-blind comparative study using enalapril maleate as a control.

OBJECTIVE: To assess the value of using imidapril hydrochloride (ACE/TA-6366), a long-acting angiotensin converting enzyme (ACE) inhibitor developed in Japan, to treat patients with essential hypertension. PATIENTS AND METHODS: A double-blind, comparative, phase III study was carried out using enalapril maleate as a control, with a 4-week observation period and a 12-week treatment period. Both drugs were started at a dose of 5 mg once a day, increasing to 10 mg in patients whose antihypertensive response was insufficient after 4 weeks. The study included 231 outpatients aged 30-74 years; of these, 108 in the imidapril group and 115 in the enalapril group were assessed. There were no differences in background factors between groups. RESULTS: An adequate antihypertensive effect was observed in 71.3% (77/108) in the imidapril group in in 66.1% (76/115) in the enalapril group, with no significant difference between groups. The pulse rate was unchanged in both groups. The drug had no adverse effects in 86.1% (93/108) of the imidapril group and 79.1% (91/115) of the enalapril group, with no significant difference between groups. Adverse drug effects were observed din 5.6% (6/108) of the imidapril group and 12.2% (14/115) of the enalapril group. Cough was the most frequent side effect, reported in 0.9% (1/108) of the imidapril group and 7.0% (8/115) of the enalapril group. Other side effects were reported in 4.6% (5/108) of the imidapril group and 5.2% (6/115) of the enalapril group. Abnormal laboratory values were observed in 3.7% (4/108) of the imidapril group and 0.9% (1/115) of the enalapril group. CONCLUSIONS: Imidapril showed excellent clinical efficacy and safety compared to enalapril. The low incidence of cough is of particular interest.

Adult↗
PubMed1995

Blood pressure sensitivity to salt, calcium metabolism and insulin sensitivity in essential hypertension.

1. To reveal the mechanism responsible for the increase in blood pressure (BP) response to high salt intake in salt-sensitive essential hypertensives, pressor responses to angiotensin II and norepinephrine on high and low salt diet, influence of high salt intake on calcium metabolism and insulin sensitivity were studied in essential hypertensive and in normotensive subjects with or without family history of hypertension. 2. Pressor responses to angiotensin II and norepinephrine were significantly increased in salt-sensitive essential hypertensives irrespective of high or low salt diet. 3. In normotensive subjects with positive family history, high salt diet elevated BP in association with an increase in urinary calcium excretion. This observation, however, was not shared by the normotensive subjects with negative family history of hypertension. In the normotensive subjects with positive family history of hypertension, the cytosolic calcium concentration in platelets was significantly higher than in those with negative family history. A significant correlation between the cytosolic calcium concentration and elevation of BP was also observed. 4. In normotensive subjects with family history of hypertension, insulin sensitivity was decreased and correlated negatively with the cytosolic calcium concentration. 5. These results suggest that in salt-sensitive essential hypertensives increased pressor responses to angiotensin and norepinephrine and elevation of BP as well as insulin resistance may result from inherited abnormalities of intracellular calcium metabolism.

Aged↗
PubMed1995

Blockade of the renin-angiotensin system in heart failure in conscious dogs.

OBJECTIVE: To study the different cardiac and renal hemodynamic effects of an angiotensin converting enzyme inhibitor and an angiotensin II receptor antagonist in experimental heart failure in conscious dogs. DESIGN AND METHODS: We compared the effects of the angiotensin converting enzyme inhibitor, captopril, with those of the angiotensin II (Ang II) subtype-1 receptor antagonist, losartan, on hemodynamics and hormonal changes in congestive heart failure by rapid ventricular pacing on conscious dogs. Furthermore, we characterized the Ang II receptors in canine heart, using the canine cardiac membrane fraction in heart failure. RESULTS: Acute intravenous administration of captopril improved the cardiac output by 19% (P < 0.01) but losartan did not, although blockade of the renin-angiotensin system by losartan (1.1 mumol/kg) or captopril (0.69 mumol/kg) induced similar changes in the plasma renin activity, norepinephrine and arginine vasopressin, and a similar decrease in mean arterial pressure (-10 mmHg). Renal blood flow was increased by either losartan or captopril. In the binding study, losartan produced a single displacement curve (IC50 = 0.25 mumol/l), while the Ang II subtype-2 (AT2) receptor antagonist PD123319 did not, indicating that the predominant Ang II receptor is type-1 (AT1) in canine heart. Neither the ratio of AT1 to AT2 receptors nor the receptor density changed with the development of heart failure. CONCLUSIONS: The lack of effect of losartan on cardiac output may be the result of its inability to block non-AT1 receptor-mediated Ang II activities adequately. Captopril may improve cardiac output by means of mechanisms not mediated by Ang II, such as locally increasing bradykinin.

Angiotensin II↗
PubMed1994

Role of nitric oxide in regulation of baroreceptor reflex.

The possible role of nitric oxide (NO) on modulating sympathetic nerve activity through its action on baroreceptor reflex arc was investigated. L-Arginine, a precursor of NO, and NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, were separately infused intravenously in increasing doses in 126 pentobarbital-anesthetized rabbits. Mean arterial pressure (MAP), heart rate (HR), aortic nerve activity (ANA), cervical (CSNA) and renal sympathetic nerve activities (RSNA) were recorded. L-Arginine infusion decreased MAP (P < 0.05), ANA (P < 0.05), CSNA (P < 0.05) and RSNA (P < 0.05) without changes in HR. Infusion of D-arginine, an enantiomer of L-arginine, and simultaneous infusion of L-arginine and L-NMMA, did not elicit such changes. L-NMMA infusion increased MAP (P < 0.05) and ANA (P < 0.05) and decreased HR (P < 0.05), while it tended to increase CSNA and RSNA without significance. Infusion of L-arginine or L-NMMA did not alter the slope of ANA, CSNA, RSNA, or HR in relation to MAP. These results suggest that NO modulates efferent sympathetic nerve activity, not by altering the afferent or efferent limbs of the baroreceptor reflex arc, but by interacting with the sympathetic pathway in the central nervous system.

Afferent Pathways↗