ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The innervation of the kidney serves to influence the function of its component parts, for example, the blood vessels, the nephron (glomerulus, tubule), and the juxtaglomerular apparatus. Alterations in efferent renal sympathetic nerve activity produce significant changes in renal blood flow, glomerular filtration rate, the reabsorption of water, sodium, and other ions, and the release of renin, prostaglandins, and other vasoactive substances. These functional effects contribute significantly to the renal regulation of total body sodium and fluid volumes with important implications for the control of arterial pressure. The renal nerves, both efferent and afferent, are known to be important contributors to the pathogenesis of hypertension. In addition, the efferent renal nerves participate in the mediation of the excessive renal sodium retention, which characterizes edema-forming states such as congestive heart failure. Thus, the renal nerves play an important role in overall cardiovascular homeostasis in both normal and pathological conditions.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The cardiovascular effects of centrally administered cholinomimetics were examined in conscious Long-Evans and Brattleboro rats. Carbachol (1 μg/kg) or physostigmine (50 μg/kg) induced a long-lasting increase in blood pressure and a decrease in heart rate in Long-Evans rats whereas no bradycardia was observed in Brattleboro rats, and the pressor response was significantly less than that in Long-Evans rats. The cardiovascular responses to nicotine (30 μg/ kg) in Brattleboro rats were not different from those in Long-Evans rats. Intravenous vasopressin antagonist, d(CH2)5Tyr(Me) arginine vasopressin, significantly attenuated the pressor response and eliminated the bradycardic response to carbachol hi Long-Evans rats. However, the pressor response to carbachol in Brattleboro rats was still significantly less than that in Long-Evans rats treated with vasopressin antagonist. Intravenous phentolamine partially inhibited the pressor response to carbachol in Long-Evans rats and completely eliminated it in Brattleboro rats. Combined intravenous treatment with phentolamine and vasopressin antagonist completely eliminated the pressor response to carbachol in Long-Evans rats. Centrally administered methylatropine eliminated either the hypertensive or bradycardic response to carbachol in Long-Evans rats. These results indicate that the pressor and bradycardic response to carbachol or physostigmine is mediated by the central muscarinic receptor mechanism. Hypertensive response to intracerebroventriculaiiy administered carbachol in normal rats is mediated both by an increase in central sympathetic outflow and in circulating vasopressin. The bradycardia seems to be mediated mainly by vasopressin.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Abnormal platelet function may contribute to the complications of essential hypertension. We have studied the kinetics of platelet aggregation induced by adenosine diphosphate (ADP) or epinephrine, plasma β-thromboglobulin, and basal, cytosolic, and free calcium, as correlates of platelet function. Fifteen untreated patients with essential hypertension and without detectable atherosclerosis, 18–40 years old, were compared with 30 matched normotensive control subjects. Maximal rates of platelet aggregation (Vmax) with ADP and epinephrine were significantly higher in patients than in control subjects (p< 0.03), as assessed by quenched-flow aggregometry. However, significance was lost when Vmaxwas corrected for the platelet count. Paradoxically, the activation constants (Ka) for ADP were higher in patients than in control subjects (p< 0.03). With ADP as the inducing agent, onset time (t) or lag period before aggregation begins was longer in patients than in control subjects (p< 0.02). β-thromboglobulin levels, an index of in vivo platelet activation, were not significantly different between the two groups (p= 0.13). The mean platelet cytosolic free calcium concentration was higher in patients (213±19 nM) than in control subjects (172±14 nM), but this difference was not statistically significant (p= 0.07). However, there was a close correlation between the free calcium level and systolic, diastolic, and mean blood pressure (p< 0.003,p< 0.04,p< 0.004, respectively). No difference in platelet volume between the two groups was found. Our data suggest that platelets in the early stages of essential hypertension display an overall increased aggregation potential but a diminished sensitivity to ADP. The tendency toward elevated calcium suggests that in hypertensive patients the platelets circulate in an already activated state; this occurrence could contribute to acceleration of atherosclerosis.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

There are differences in the renal handling of sodium between spontaneously hypertensive rats (SHR) and their normotensive controls. We investigated whether this difference may be associated with changes in plasma and tissue atrial natriuretic factor (ANF) levels and with alterations in glomerular ANF receptors at 4, 8, 12, and 16 weeks of age. Age-matched Wistar-Kyoto (WKY) and Wistar rats were used as normotensive controls. Systolic blood pressure was higher in SHR at 8, 12, and 16 weeks, and cardiac hypertrophy was also present in these animals at 4 weeks. Plasma ANF C- and N-terminal concentrations were greater than in both normotensive groups at 8 and 16 weeks. ANF in the right atrium was higher in SHR than in WKY rats and identical to that in the Wistar group at 4 and 8 weeks. ANF in the left atrium was lower in SHR than in both control groups at week 12. No differences were found in ventricular ANF content. The density of glomerular ANF binding sites increased with age in WKY and Wistar rats but not in SHR. At weeks 8, 12, and 16, both normotensive groups had a higher density of binding sites than SHR, but binding site affinity was greater in SHR at weeks 8 and 12. After incubation with increasing concentrations of ANF, the production of cyclic guanosine monophosphate (cGMP) by isolated glomeruli from 16-week-old rats was lower in SHR than in both normotensive groups. We conclude that the development of hypertension in SHR is associated with higher plasma ANF levels and decreased glomerular ANF receptor density and glomerular cGMP production. Through modulation of ANF glomerular receptors, ANF in SHR, when compared with normotensive counterparts, may contribute to the difference in renal sodium handling.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The effect of glococorticoids on the dopamine (DA)-mediated cyclic adenosine monophosphate (cAMP) by intact vascular smooth muscle cells (VSMC) was studied in rats. Cultured VSMC were obtained from renal arteries of 14-week-old Wlstar-Kyoto rats by explant method. Micromoiar concentrations of dexamethasone (DEX) pretreatment for 48 hours potentiated DA-mediated response without any change of affinity constant. However, micromoiar concentrations of aldosterone pretreatment for 48 hours had almost no effect on DA-mediated response. The DEX-induced facilitation began at 6 hours and reached maximum at 24 hours after DEX administration in a dose-dependent manner. Inhibitors of protein and RNA synthesis blocked this glucocorticoid effect. The basal activity of adenylate cyclase in DEXtreated cells was twofold higher than that in control cells. Treatment of VSMC with DEX increased cholera toxin-stimulated and forskolin-stimulated adenylate cyclase activity. However, pertussis toxin treatment did not augment or reduce the effect of DEX treatment. These results suggest that glucocorticoids increase DA-mediated cAMP formation by VSMC through glucocorticoid type II receptors and the induction of protein synthesis and that the activation of the catalytic unit may play some role in this facilitation.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Long-term effects of a novel angiotensin converting enzyme (ACE) inhibitor, CS-622, on Ca2+-dependent tone in aortic smooth muscles of spontaneously hypertensive rats (SHR) were examined. CS-622 (3 or 10 mg/kg/day), when orally administered to SHR for 21 weeks, exhibited a dose-dependent antihypertensive action. In Krebs-Henseleit solution, removal of Ca2+caused much greater relaxation in aortas excised from control SHR than those from SHR treated with CS-622. Restoration of Ca2+from zero to 2.5 mM elicited a marked contraction in aortas from control SHR but only a small contraction in aortas from both CS-622-treated SHR and normotensive Wistar-Kyoto rats. These findings suggested that myogenic tone that resulted from increased Ca2+permeability in aortas of SHR was suppressed by long-term treatment with CS-622. The aortic tone from the individual rats correlated well with systolic blood pressure in both CS-622-treated and control SHR. The exaggerated myogenic tone in aortas of SHR was attenuated in the medium containing nicardipine but was not altered in the presence of CS-622 diacid (active form of CS-622) at a concentration high enough to fully inhibit aortic ACE. The myogenic tone in normal Ca2+concentration was not decreased in aortas excised from SHR treated with hydralazine (5 mg/kg/day) for 21 weeks. We conclude that after prolonged administration CS-622 reduced the high vascular tension resulting from increased Ca2+permeability of vascular smooth muscle membrane in SHR and that the restoration of normal Ca2+permeability of vascular smooth muscles may underlie long-term antihypertensive action of ACE inhibitors.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Comparative studies have shown that cultured vascular smooth muscle cells from spontaneously hypertensive rats (SHR) proliferate to a higher cell number, grow to a greater density, and have greater specific growth rate, particularly at a higher saturation density, than those of the normotensive Wistar-Kyoto (WKY) control rats. The growth difference was not due to varying cell survival nor to attachment ability after passage. The degree of DNA synthesis was estimated by [3Hlthymidine incorporation into newly synthesized DNA. [3H]thvmidine uptake increased with escalating concentrations of calf serum and reached a plateau at 5% calf serum hi WKY rats, whereas an excessive, continuous rise was observed in SHR with up to a 20% concentration. [3H]thymidine incorporation into newly synthesized DNA was tested after stimulation by platelet-derived growth factor and epidermal growth factor. A significantly higher amount of newly synthesized DNA in vascular smooth muscle cells from SHR was noted when the cells were stimulated by platelet-derived growth factor or epidermal growth factor alone, and their simultaneous addition did not significantly change the 50% effective concentration but heightened the maximal response. These data provide evidence of increased aortic smooth muscle cell proliferation from aortas of SHR after mitogen stimulation and suggest a defect in growth stimulatory-inhibitory control.

ISSN:0194-911X    

出版商:OVID    

年代:1989

数据来源: OVID