摘要:

SUMMARY The influence of the renln-angiotensin system on individual kidney function of two-kidney, one clip Goldblatt hypertensive (GH) rats was evaluated by determining renal functional responses during intravenous infusion of converting enzyme inhibitor (CEI) (SQ 20,881, 0J rag/100 g-hr) for 3.5 bourn. Rats were made hypertensive by placing a 0.25 mm silver clip on the right renal artery 3-4 weeks prior to study. Normal rats and GH rats were prepared to allow urine collections from each kidney. Mean arterial pressure of GH rats fell significantly from preinfusion levels of 153 ± 7 to 126 ± 4 mm Hg during CEI infusion. Despite this decrease in arterial pressure, the nondipped kidneys with reduced renal renin activity (14 ± 5 vs 293 ± 40 ng Al/mg-hr in the clipped kidney) exhibited dramatic increases in gtomerular filtration rate (GFR) (from 1.45 ± 0.06 to 2.56 ± 0.35 ml/mln), urine flow (4.82 ± 0.71 to 9.11 ± 1.19 μl/mln), sodium excretion (0.10 ± 0.02 to 1.15 ± 0.39 μEq/mln), fractional sodium excretion (0.05% ± 0.02% to 0.43% ± 0.18%), and potassium excretion (0.94 ± 0.08 to 2.50 ± 0.55 /<Eq/mln). Significant arterial-pressure-associated decreases In GFR, urine flow, and salt excretion were observed in the clipped kidney. In normal rats, CEI infusion produced reductions in arterial pressure and increases in GFR, urine flow, and sodium excretion that were of smaller magnitude than those observed in the nondipped kidneys of GH rats. Plasma renin activity was significantly higher in GH rats than in normal rats (24.0 ± 2.7 vs 12.8 ± 3.4 ng AI/mMir). The augmented renal responses to CEI by the nondipped kidney suggest that elevated circulating angiotensin levels exert a substantial influence on hemodynamic and excretory function of these kidneys even though intrarenal renin activity is markedly reduced. This influence may lead to fluid and electrolyte retention and may partially explain the apparent failure of the nondipped kidney to prevent the development of hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY To assess the interaction between adrenergic activity and blood pressure regulation in patients with chronic renal failure, plasma norepinephrine (NE) and plasma renin activity (PRA) were measured before and after rigorous ultrafiltration. The significance of PRA was further assessed by anglotensin blockade with saralasin. Two patterns of response were defined: nine patients had low levels of PRA before and after hemodialysis. These patients showed a net fall in norepinephrine and no angiotensin dependence at any time. Failure to stimulate either PRA or norepinephrine was also observed during periods of marked hypotension. Seven other patients had higher PRA, which rose during bemodialysis. This was associated with an increase in NE and postdialysis angiotensin dependence. Patients experiencing hypotension in this group showed a sharp rise in NE, suggesting baroceptor-mediated adrenergic stimulation. In all patients sustaining hypotension during therapy, postdialysis PRA was closely correlated with NE. These results Indicate that hemodialysis mobilizes the renin-angiotensln system to maintain hypertension in a greater proportion of dialysis patients than previously supposed and that impaired renin release following hypotension may represent uremic autonomic dysfunction.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY The steroidogenic properties of a glycoprotein fraction (urinary ASF), isolated from normal human urine, were studied in collagenase-dlspersed rabbit adrenal capsular cells to 1) define the requirements for its steroidogenic activity, and 2) assess its site and mode of action. When incubated with adrenal cell suspension at 37°C for 2 hours, urinary ASF induced dose-related increases in both aldosterone and corticosterone production. However, urinary ASF was less potent (EDU= 10−11M) than either angiotensln II (EDM= 8 × 10−11M) or ACTH (EDM= 4 × 10−9M). Increases in cyclic AMP accompanied the steroidogenic response to ACTH but not to either urinary ASF or All. Deprivation of potassium in incubation media or the addition of ouabaln (1 mM) during incubation completely inhibited the steroidogenic response to either urinary ASF, ACTH, or All. Like ACTH and All, urinary ASF increased conversion of corticosterone to aldosterone. Specific competitive antagonist of All (Sar1, Thr3AH) and ACTH ([11e9]ACTH1−34) did not prevent the ASF-induced increase in aJdosterone production. These results suggest that urinary ASF is readily distinguishable from ACTH. Although it shares similar steroidogenic properties with All, the inability of All antagonist to block its effects suggests that it acts at a separate receptor site.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY Decreased actirity of the electrogenlc sodium pump of vascular smooth muscle has been reported in several forms of experimental hypertension and may play an important role in basic disease mechanisms. It has been proposed that such pump suppression may characterize volume-expanded forms of hypertension. The present investigation tested this latter hypothesis. Sodium pump activity was assessed in vitro in sodium-loaded tail artery and thoracic aorta freshly excised from Dahl salt-sensitive (S) and saltresistant (R) rats on low (0.4%) or high (8%) NaCI diets for 5 to 7 weeks. Rubidium (uRb) uptake in the absence (total uptake) and presence (ouabain-insensitive uptake) of l.OmM ouabain was measured and ouabain-sensitive uptake (nmole/mg dry weight/10 mln) was calculated. In S rats, salt feeding was accompanied by elevation of arterial pressure, cardiac hypertrophy, increases of 20% to 30% in total blood volume, and increases in the ouabain-sensitive, ouabain-insensitive, and total uptakes in the aorta, but no significant change in uptakes in the tail artery. However, ouabaln-sensitire uptake in the tail artery of all S rats exceeded that in R rats. There was no evidence of a decrease in vascular sodium pump activity accompanying hypertension in either artery. Therefore, the results of this study provide no evidence in support of the hypothesis that pump suppression in vascular smooth muscle characterizes volume-expanded forms of hypertension. It is unlikely that the observed increases in vascular pump activity in S rats reflected intracellular sodium concentrations higher than those in the control rats. Rather, increases in the numbers of pump molecules or in their turnover rate are probably involved.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY Angiotensin II, when given into the vertebral arteries, acts at the area postrema to augment central sympathetic vasomotor activity. The mechanism of action is unknown but recent evidence implicates an interaction with the opiate system. In dogs anesthetized with chloralose either alone or in combination with morphine, naloxone blunted the pressor response to vertebrally administered angiotensin II by 50%. Addition of morphine to dogs anesthetized with chloralose only doubled the pressor response to identical doses of angiotensin II. On the other hand, the magnitude of the pressor responses to intravenously infused angiotensin II were unaltered by either naloxone or morphine. Likewise, responses to noreplnephrine given vertebrally and intravenously were not similarly affected. Therefore, naloxone-induced changes in vascular responsiveness were not responsible for the altered sensitivity of the area postrema to angiotensin II following blockade of endogenous opiates. The data suggest that there exists a previously unrecognized interaction of the endogenous opiate system in the medulla in mediating the pressor effects of angiotensin II at the level of the area postrema.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY The urinary excretion of sodium, potassium, and water during three 24-hour periods were related to blood pressure in a sample of 49-year-old men. Of 3205 49-year-old men liring in Goteborg, 2376 (74%) took part in the blood pressure screening, and, of these, 120 subjects having blood pressures from the lowest to the highest were selected by systematic sampling based on diastolic blood pressure. Only subjects who were not on antihypertensive treatment were included. Results showed a marked day-to-day variation in sodium excretion, with between-days r values of 0.23-0.64. The variation was less for two consecutive days than for two nonconsecutive days. The mean urinary excretion and the diurnal rhythm of sodium, potassium, and water did not differ significantly among normotensive, borderline, and hypertensive subjects. Over a wide range of blood pressures, no correlation was found between blood pressure and the urinary excretion of sodium, potassium, or water. In the low blood pressure range, however, there was a significant positive correlation between blood pressure and urinary sodium excretion (R = 0.46,p< 0.01; R = Spearman's coefficient of rank correlation).The large intraindiridual variation in sodium excretion and blood pressure makes it difficult to estimate an individual's mean values. Furthermore, there are limitations in drawing longitudinal conclusions from crosssectional data. With these methodological problems in mind, our findings indicate that salt intake influences blood pressure in a part of the normotensire population, but do not lend support to the hypothesis that habitual salt intake might be of major importance for the blood pressure level in mild to moderate essential hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY Effects of hemodialysis on extracellular fluid volume distribution, left ventricular volumes, and cardiac output were determined In patients with end-stage renal disease (n = 19). Distribution of extracellular fluid loss from hemodialysis differed widely among patients, so that weight change correlated weakly with contraction of total blood volume (index of determination 29%,p< 0.05). End-diastolic volume (EDV) decreased from 150 ± 49 ml (mean ± SD) to 118 ± 42 ml,p< 0.001; stroke volume (SV) decreased from 108 ± 36 to 86 ± 33 ml (p< 0.001) without change in ejection fraction (from 0.73 ± 0.09 to 0.74 ± 0.11).A significant correlation was found between total blood volume (TBV) and EDV before (r= 0.66,p< 0.005) and after dialysis (r= 0.61,p< 0.01). The correlation between TBV and SV was highly significant before (r= 0.78,p< 0.001) and after dialysis (r= 0.66,p< 0.005), but there was no correlation between change in TBV and change in EDV or in SV. The ratio of EDV to TBV (EDV/TBV X 100) was reduced significantly from 3.49 ± 0.92 to 3.06 ± 0.97,p< 0.001). There results suggest that, although intravascular volume was the major determinant of cardiac output in dialyzed patients, the postdialysis reduction in cardiac output might be related more to the relocation of blood volume than to the absolute degree of blood volume contraction.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY Blood pressure response to hemodialysis was investigated in IS patients with end-stage kidney disease; mean arterial pressure was unchanged in fire (Group 1) and reduced 10 mm Hg in 10 (Group 2). The two groups did not differ significantly with regard to either biochemical rallies or hemodynamic indices before dialysis, and both sustained comparable reduction in body weight, total blood volume, and cardiac output following dialysis. Heart rate remained unchanged In both. The only significant difference between the two was the response of total peripheral resistance (TPR) to fluid depletion. TPR rose adequately in Group 1 but was unchanged in Group 2 (7.5 ± 2.2 (SE) VS 0.7 ± 1.1 units,p< 0.02S) despite equal fall in cardiac output in both (881 ± 212 vs 890 ± 173 ral/m, p > 0.10). Thus, differences in arterial pressure response to fluid loss by hemodialysis could be due to impaired autonomic control of resistance vessels; this abnormality might not be revealed by tests of baroreceptor activity that depend only on heart rate responses to blood pressure variations.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY Recordings of multi-unit sympathetic activity were made from muscle branches of the peroneal nerve during i.v. bolus injection of 100 to 275 pg clonidine in seven hypertensive patients. Blood pressure was reduced in all patients, but sympathetic activity and heart rate could either increase or decrease. When plasma levels of clonidine were low, sympathetic activity tended to Increase, and when plasma levels were high, activity tended to decrease. Irrespective of whether mean level of sympathetic activity increased or decreased with the fall in blood pressure level, transient fluctuations of blood pressure continued to cause dynamic baroreflex modulation of the sympathetic outflow. It is suggested that the drug influences sympathetic outflow by a combination of central and peripheral effects.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

SUMMARY The correlation between the degree of conjugation of plasma noreplnephrine (NE) and epinepbrine (E) and the clinical features of sympathetic hyperactivity was studied in 38 essential hypertensive patients from a referral population biased toward pheochromocytoma (19 of them suspected of this diagnosis on clinical grounds). The patients were separated into two groups: 15 with subnormal plasma conjugated NE + E, i.e., below 0.23 ng/ml (Group 1), and 23 patients above this limit (Group 2). Patients clinically suspected of pheochromocytoma represented 93% of the patients in Group 1 but only 21% in Group 2.Group 1 patients, compared to those of Group 2, had: 1) higher baseline plasma free NE + E (0.51 ± 0.07 ng/ml vs 0.30 ± 0.04 ng/ml,p< 0.02); 2) an increase in plasma free NE + E in response to stressful sampling (148% ± 59%,p< 0.05 vs 58% ± 30%), and a more pronounced response (p< 0.05) to glucagon administration; 3) higher free NE + E and DA in the regional samples received during catheterization while conjugated NE and/or E were usually absent; and 4) a higher spread between maximum and minimum blood pressure and a higher maximum pulse rate recorded as well as the index of sympathotonia. All patients combined had the 'maximum pulse rate correlated negatively (p< 0.005) with conjugated NE + E, but positively (p< 0.005) with free NE + E. The clinical and biochemical similarity to pheochromocytoma was particularly striking in some Group 1 patients who had a selective defect in E conjugation; some of them had a history of surgical exploration for the lesion, without result.The association of subnormal conjugated plasma NE and/or E with moderately elevated plasma NE + E and a more frequent pseudopheochromocytoma presentation may result from inadequate conjugation, and hence inactivation of NE and/or E. Excessive free catecholamines would account for the clinical symptoms and for tbe fact that the patients are well controlled by treatment with beta-adrenerglc blocking agents, either alone or in combination with a-blockers. Awareness of tbe existence of this variety of essential hypertension can obviate unnecessary surgery for wrongly suspected pheochromocytoma.

ISSN:0194-911X    

出版商:OVID    

年代:1981

数据来源: OVID