Renin-angiotensin-aldosterone system and thromboxane A2/prostacyclin in normotensive and hypertensive black Zimbabweans.
Fourteen normotensive and 14 hypertensive black men with mild essential low-renin hypertension were examined during two protocols producing sodium depletion (less than 40 mmol sodium diet per day) for 5 days, followed by sodium loading (300 mmol sodium diet per day) for another 5 days. Changes in plasma renin activity, urinary aldosterone excretion, and excretion rates of stable breakdown products of thromboxane A2 (thromboxane B2) and prostacyclin (6-keto PGF1 alpha) were simultaneously assessed by radioimmunoassay. On the basis of low-renin status and paradoxically normal aldosterone excretion in both normotensives and hypertensives, thromboxane B2 excretion was increased by 14% (not significant); 6-keto PGF1 alpha was significantly decreased by 47% in the hypertensives compared to the normotensives. As a result, thromboxane B2/6-keto PGF1 alpha ratio was significantly increased from 1.29 +/- 0.10 in the normotensives to 2.78 +/- 0.12 in the hypertensive patients. The same ratio increased significantly after sodium loading in both groups, but more distinctly in the hypertensives (40%). Prostacyclin is a vasodilator, a natriuretic, and a potent inhibitor of platelet aggregation. Thromboxane A2 has opposite effects. The impaired prostacyclin biosynthesis we found in the hypertensive patients could account for the increased vascular resistance and some complications typical for hypertensive state.
Somova
L I
LI
Department of Physiology, University of Zimbabwe, Harare.
Mufunda
J J
JJ
D000328:Adult; D000450:Aldosterone / Q000652:urine; D044383:Black People; D011464:Epoprostenol / Q000378:metabolism* / Q000502:physiology / Q000652:urine; D005069:Evaluation Studies as Topic; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000378:metabolism* / Q000652:urine; D008297:Male; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000009:adverse effects* / Q000378:metabolism; D013928:Thromboxane A2 / Q000378:metabolism* / Q000502:physiology / Q000652:urine; D015030:Zimbabwe
D012982:Sodium, Dietary; D000450:Aldosterone; D013928:Thromboxane A2; D011464:Epoprostenol; D012083:Renin