ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Several laboratories have reported that the activities of sodium-lithium countertransport are increased in red blood cells from patients with essential hypertension. Based on the many similarities between this transport system and the renal sodium-proton exchanger, a hypothesis has been put forth in the literature that increased red blood cell sodium-lithium counter-transport activity may be a marker for increased sodium-proton exchange activity in the renal proximal tubule. The present studies were designed to test the hypothesis that sodium-lithium countertransport in red blood cells from humans or rabbits is mediated by the same transport mechanism that mediates sodiumproton exchange in the renal brush border from those species. Similar to what has been reported for the rabbit, the present studies show that an amiloride-sensitive sodium-proton exchanger is present in human renal brush border vesicles. However, Na+-Li+countertransport in human and rabbit red blood cells, assayed under several different conditions, was not inhibited by amiioride. In agreement with what has been reported for humans, the present studies show that extracellular proton-stimulated sodium efflux is inhibited by amiioride in rabbit red blood cells. These data demonstrate a difference (amiioride sensitivity) between the red blood cell sodium-lithium countertransporter and the renal brush border sodium-proton exchanger in humans and rabbits. These experiments detract from the hypothesis that increased red blood cell sodium-lithium countertransport activity in patients with essential hypertension is a marker for increased sodium-proton exchange activity In the renal brush border.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effects of stress on leukocyte membrane sodium efflux rate constant and plasma norepinephrine levels were studied before and during cold pressor test in normotensive subjects with and without a family history of hypertension. After 20 minutes of supine rest, no significant differences in total, ouabain-resistant or ouabain-sensitive sodium efflux rate constants were apparent between the two groups. In normotensive subjects with no family history, there was no significant change in any efflux rate constant during cold pressor test, although there was a highly significant negative correlation between change in total efflux rate constant and change in norepinephrine levels (r = −0.82,p< 0.01,n= 12). During cold pressor test in subjects with a family history of hypertension, there was a significant rise in the ouabain-resistant efflux rate constant (1.5 ± 0.1 vs 1.0 ± 0.1 hr;p< 0.01,n= 10); this level was also significantly higher than that in control subjects (p< 0.002). In this group, the ouabain-sensitive efflux rate constant fell slightly but not significantly (1.8 ± 0.2 vs 2.1 ± 0.2 hr-' a = 10). These results suggest that stress in the form of a cold stimulus produces qualitative differences in leukocyte cation transport in normotensive offspring of hypertensive patients as compared with subjects without such a family history.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effects of the calcium antagonist diltiazem on diastolic blood pressure and various parameters of erythrocyte membrane cation transport were evaluated in hypertensive patients with diastolic blood pressure between 95 and 110 mm Hg in a placebo-controlled, double-blind parallel study. Twenty-one patients completed the study; 13 received placebo, while 8 received diltiazem. Diastolic blood pressure, intracellular sodium and calcium concentrations, ouabain-sensitive Na+, K+-adenosine triphosphatase (ATPase) activity, and net sodium efflux and potassium influx across red blood cell membranes were examined in both groups at the end of placebo run-in, at the end of the titration phase, and at the completion of study. In the placebo group, none of the parameters changed significantly. In the drug-treated group, diastolic blood pressure declined by approximately 10% (placebo, 95.1 ± 8.9; drug-treated, 86.9 ± 4.9 mm Hg;p< 0.03) at the end of the study. There were also reductions in intracellular sodium (placebo, 7.9 ± 1.8; drug-treated, 5.2 ± 0.4 mmol/L cells;p< 0.002) and calcium (placebo, 13.5 ± 1.6; drug-treated 10.8 ± 3.3 Mmol/L cells;p< 0.03) concentrations, accompanied by a simultaneous rise in the activity of the ouabain-sensitive Na+, K+-ATPase of erythrocyte membranes (placebo, 7.1 ± 1.1 × 10-J; drug-treated, 9.0 ± 0.6 × 10–2 fiM inorganic pbosphate/hr/mg;p< 0.001) at the end of the study. However, no significant change in the ouabaininsensitive moiety of the ATPase pump was found. Diltiazem treatment increased net sodium efflux and potassium influx. It is concluded that diltiazem reduces diastolic blood pressure of hypertensive subjects. Erythrocyte studies indicate that diltiazem not only blocks entrance of calcium into the cells but may also stimulate Na+, K+-ATPase activity, resulting in reduction in intracellular sodium concentration, thus suggesting a possible dual mechanism for its antihypertensive effects.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Numerous studies have reported the mean value for Na+-Li+countertransport to be increased in red blood cells from patients with essential hypertension. Although concomitant variables including age, body size, national origin, geographic location, gender, and family history of hypertension may affect Na+-Li+countertransport values, most case-control studies have failed to assess the contribution of these factors to the differences in Na+-Li+countertransport between hypertensive and normotensive groups. The present study was undertaken to provide estimates of Na+-Li+countertransport in hypertensive and normotensive subjects after taking into account these potentially confounding sources of variation. In 187 subjects undergoing medical evaluation at the Mayo Clinic, Rochester, MN, the combined effects of variation in age, height, and weight accounted for 20.6% of the interindividual variability in Na+-Li+countertransport. After adjustment to remove variability due to these concomitants, differences in national origin, region of birth, and place of current residence made no additional contribution to variability in this trait. There was no significant difference in mean adjusted Na+-Li+countertransport between men and women (0.41 ± 0.17 vs 0.40 ± 0.12 [SD] mmol Li efflux/L red blood cells/hr; a = 107). The mean value for adjusted Na+-Li+countertransport was significantly greater (p s 0.001) in subjects with essential hypertension (0.44 ± 0.15 mmol/L red blood cell/hr; a = 104) compared with normotensive subjects (0.31 ± 0.07 mmol/L red blood cells/hr;n= 39) or subjects with borderline blood pressure elevation (0.35 ± 0.11 mmol/L red blood cells/hr;n= 21). Subjects with a family history of hypertension in at least one parent or full sibling had significantly higher (p< 0.02) Na+-Li+countertransport values (0.42 ± 0.16 mmol/L red blood cells/hr;n= 111) than those with no family history of hypertension (0.37 ± 0.13 mmol/L red blood cells/hr;n= 76). These results suggest that increased mean Na+-Li+countertransport in hypertensive subjects in this sample cannot be attributed to confounding effects of variation in age, body size, gender, national origin, birthplace, or residence. Forty-eight percent of subjects with essential hypertension had adjusted Na+-Li+countertransport values above the range observed in normotensive controls.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effect of the intravenous administration of dihydroergotoxine (6 μg/kg) on arterial blood pressure, heart rate, and plasma concentrations of norepinephrine and 3,4-dihydroxyphenylacetic add (the deaminated dopamine metabolite) was studied in 20 subjects with essential hypertension (8 men and 12 women aged 32–68 years old, World Health Organization Class I-O). In supine resting subjects, dihydroergotoxine significantly decreased systolic blood pressure (from 175 ± 5 to 156 ± 4 mm Hg;p< 0.001), diastolic blood pressure (from 109 ± 4 to 95 ± 3 mm Hg;p< 0.001), and heart rate (from 71 ± 2 to 63 ± 2 beats/min;p< 0.001) as compared with the results of placebo treatment. Moreover, dihydroergotoxine reduced plasma levels of norepinephrine (from 368 ± 39 to 238 ±33 pg/ml;p< 0.001) and 3,4-dihydroxyphenylacetic acid (from 1.57 ±0.21 to 1.22 ±0.13 ng/ml;p< 0.01). The time course of the blood pressure decrease paralleled that of plasma norepinephrine concentration. Dihydroergotoxine did not suppress the cardiovascular and plasma norepinephrine response to standing. The effect of domperidone, a peripheral presynaptic dopamine receptor antagonist, on dihydroergotoxine response was studied in six of the 20 subjects (3 men and 3 women 48–64 years old). The intravenous administration of domperidone (0.3 mg/kg) prevented the dihydroergotoxine-induced reduction in blood pressure and heart rate and the fall in plasma norepinephrine and 3,4-dihydroxyphenylacetk acid levels. Domperidone administered alone failed to significantly modify any measured variables. These results suggest that the antihypertensive effect of dihydroergotoxine can be mediated by the inhibition of norepinephrine release from peripheral sympathetic nerves secondary to the activation of presynaptic dopamine receptors.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

To identify a physiological role for renal A2adrenergic receptors, renal vascular and tubular responses to administration of graded frequencies of renal nerve stimulation or graded doses of adrenergic agonists were determined in anesthetized spontaneously hypertensive, Wistar-Kyoto, and Sprague-Dawley rats. Renal vasoconstrictor responses to renal nerve stimulation and α1-adrenergk receptor agonists (norepinephrine, phenylephrine) were inhibited by an α1-adrenergic receptor antagonist (prazosin) but not by an aradrenergic receptor antagonist (rauwolscine). A semilog plot of renal vasoconstrictor responses as fraction of control renal blood flow versus agonist dose (in nanograms) was linear with the slope, k, taken as the fractional decrease in renal blood flow per nanogram. The α1-adrenergic receptor agonists (clonidine, guanabenz) produced minimal renal vasoconstrictor responses (fractional decrease in renal blood flow per nanogram: norepinephrine, 0.011; phenylephrine, 0.003; clonidine, 0.00087; guanabenz, 0.000037). The small renal vasoconstrictor responses to clonidine and guanabenz were more inhibited by rauwolscine than by prazosin. Low frequency renal nerve stimulation produced antidiuresis and antinatriuresis without decreasing giomenilar filtration rate or renal blood flow. The antidiuretic and antlnatriuretic responses were inhibited by prazosin but unaffected by rauwolscine. The magnitude of the renal vascular and tubular responses and their adrenergic receptor mediation were not different between spontaneously hypertensive, Wistar-Kyoto, and Sprague-Dawley rats. Although increased numbers of renal α2-adrenergic receptors have been described in spontaneously hypertensive rats, these results indicate that the renal vascular and tubular responses to renal nerve stimulation and adrenergic agonists are dependent on renal α1-adrenergic receptors; renal α2-adrenergic receptors are not involved.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

A 5-year-old female Siberian husky that was diagnosed as an essential hypertensive was bred several times over a 5-year period, producing a colony of 39 offspring. Thirty of the 39 animals were subjected to biweekly systemic arterial blood pressure determinations with femoral arterial puncture and were placed into two hypertensive and two normotensive groups based on mean blood pressure: Group 1 (mean blood pressure, 128 ± 12 mm Hg), Group 2 (mean blood pressure, 121 ± 3 mm Hg), Group 3 (mean blood pressure, 114 ± 8 mm Hg), and Group 4 (mean blood pressure, 101 ± 9 mm Hg). Groups 1,2, and 3 had mean blood pressures significantly higher than that of Group 4 (p<0.05). Ten dogs (representatives from Groups 1, 2, and 3) were subjected to more detailed clinical testing including angiography, echocardiography, ophthalmic examination, plasma catecholamine and renin activity measurements, plasma lead and cadmium determinations, cerebrosplnal fluid examination, renal profile, and serum chemistry and hematological analysis. Five unrelated normotensive Siberian huskies were compared with colony dogs by using echocardiography. Groups 1 and 2 showed a clear but statistically insignificant upward trend in left ventricular wall thickness indexed against body weights when compared with that in Group 3 and in the unrelated five normal Siberian dogs. Thus, the only specific difference from group to group in the colony at the termination of this study was the difference in mean blood pressure. Based on these data, it is possible and likely that aging will reveal changes secondary to chronic primary hypertension. The pathogenesis of this hereditary disorder remains unknown.

ISSN:0194-911X    

出版商:OVID    

年代:1987

数据来源: OVID