Showing papers by "Gordon H. Williams published in 1975"

Potassium-Aldosterone-Renin Interrelationships

Abstract: The present study was performed to assess the sensitivity of the renin-angiotensinaldosterone axis to small changes in plasma potassium concentration within the physiologic range. Small increments in potassium levels were accomplished by graded constant infusions of potassium chloride over 2 h (0.17 meq/min; 0.33 meq/min; 0.5 meq/min) in 8 normal subjects on a 10 meq sodium-100 meq potassium intake. Plasma levels of aldosterone, renin activity, angiotensin II, cortisol, potassium and sodium were measured at frequent intervals. There were no significant changes observed in plasma sodium, renin activity or angiotensin II levels while cortisol levels declined in the expected diurnal pattern. During the 0.17 meq/min (10 meq/h) infusion potassium levels did not increase significantly until 120 min while plasma aldosterone levels rose significantly at 30-60 min. The mean increment above control during the lowest infusion rate was 0.2 meq/liter (5%) for plasma potassium and 13 ng/100 ml (46%) for plasma aldoster...

Response of the kallikrein-kinin and renin-angiotensin systems to saline infusion and upright posture.

Abstract: The possibility that bradykinin, a potent vasodilator, might be a physiological antagonist of the renin-angiotensin system was investigated. 11 norman subjects, ranging in age from 21 to 33 yr were studied. Seven of the subjects were given a 10 meq sodium, 100 meq potassium, 2500 ml isocaloric diet. After metabolic balance was achieved, they were infused with either 1 liter of 5 per cent glucose over 2 h or 2 liters of 0.9 per cent saline over 4 h. During the infusions, plasma renin activity (PRA), angiotensin II (A II), prekallikrein, bradykinin, and aldosterone levels were frequently determined. Plasma prekallikrein and kallikrein inhibitor did not change during the infusion of either glucose or saline. In subjects receiving saline, plasma bradykinin fell from 3.9 plus or minus 1.5 (SEM) ng/ml at 0 min to 0.93 plus or minus 0.2 at 30 min and 0.95 plus or minus 0.3 at 120 min. These changes paralleled the decrease in PRA over the same period (7.9 plus or minus 1.3 ng/ml/h to 5.6 plus or minus 0.8 at 30 min and 3.5 plus or minus 0.7 at 120 min). Similarly, A II fell from 113 plus or minus 12 pg/ml to 62 plus or minus 10 and 48 plus or minus 5, respectively, at 30 and 120 min. In contrast, the control group infused with glucose showed no change in bradykinin, A II, or PRA. Another four subjects were given a constant 200 meq sodium/100 meq potassium isocaloric diet. After metabolic balance was achieved, they were kept supine and fasting overnight. At 9 a.m. they assumed an upright position and began walking a fixed distance (200 ft) at a normal rate (3-4 ft/s). Plasma prekallikrein and kallikrein inhibitor did not change during the posture study. The plasma bradykinin rose from a base line of 0.54 plus or minus 0.01 (SEM) ng/ml to 0.96 plus or minus 0.13 at 20 min. 0.77 plus or minus 0.18 at 60 min, and 0.96 plus or minus 0.07 at 120 min. These changes parallel the increase in PRA over the same period (1.65 plus or minus 3.3 ng/ml/h to 3.6 plus or minus 0.85 at 20 min, 5.3 plus or minus 0.9 at 60 min, and 5.35 plus or minus 0.55 at 120 min). Likewise, the A II rose from 32.5 plus or minus 1.82 pg/ml to 50.8 plus or minus 3.6 at 20 min, 54.3 plus or minus 3.2 at 60 min, and 61.3 plus or minus 5.9 at 120 min. Thus, in sodium-depleted individuals, saline infusion produces a rapid fall of plasma bradykinin at a rate similar to that observed for a II and PRA. Conversely, in sodium-loaded individuals, assumption of upright posture leads to a parallel rise in A II, TPRA, and bradykinin. These studies indicate that there is a close correlation of bradykinin levels with renin activity and angiotensin II, in both acute sodium loading and assumption of upright posture, suggesting that these two systems may be physiologically interrelated.

Plasma Renin Activity and Blood Volume in Uncontrolled Diabetes: Ketoacidosis, a State of Secondary Aldosteronism

Abstract: The renin-angiotensin-aldosterone system was evaluated in two types of uncontrolled diabetes: a) diabetic ketoacidosis, and b) nonketotic hyperglycemia. In thirteen patients with ketoacidosis, mean plasma renin activity (PRA) was 58 plus or minus 12 (S.E.M.) ng. per milliliter per hour and in four patients, plasma aldosterone was 82 plus or minus 17 ng. per 100 ml. Corresponding values for upright salt-depleted subjects were 13 plus or minus 2 and 62 plus or minus 8. In eleven diabetics with nonketotic hyperglycemia (mean glucose 318 plus or minus 19 mg. per cent), mean blood volume was 4,660 ml. and PRA 2.1 plus or minus .7. After control of the diabetes (mean glucose 129 plus or minus 13) blood volume was 4,553 ml. and PRA 3.3 plus or minus 1 (NS). The results suggest that: 1) diabetic ketoacidosis is a state of severe secondary aldosteronism, 2) no significant change in blood volume or PRA occurs during short periods of hyperglycemia, and 3) insulin is not necessary for renin release.

The influence of potassium on the renal vasculature and the adrenal gland, and their responsiveness to angiotensin II in normal man.

Abstract: 1. The effect of modifying potassium intake on arterial plasma renin activity, angiotensin II and aldosterone concentrations, renal blood flow and their responses to exogenous angiotensin II has been assessed in twenty-six normal subjects. 2. Reduced potassium intake was associated with a significant increase in circulating renin activity and angiotensin II concentration and a significant reduction in renal blood flow. Conversely, a high potassium intake was associated with a significant increase in plasma aldosterone concentration and renal blood flow without alteration in plasma renin activity or angiotensin II concentration. 3. Reduced potassium intake decreased both the renal vascular and the adrenal response to infused angiotensin II. Conversely, an increased potassium intake enhanced the responsiveness of both systems. 4. The results suggest an important influence of potassium-induced renin-angiotensin system responses on both the renal vasculature and adrenal glomerulosa cell in normal man.

Aldosterone dynamics during graded exercise at sea level and high altitude

Abstract: Hormonal responses to graded exercise of eight low altitude residents were examined at sea level (SL) and after 1 (acute) and 11 (chronic) days at 4,300 m (HA). Caloric, water, and electrolyte intakes were controlled, as were temperature and humidity. Blood was sampled at rest and during light and moderate upright bicycle exercise (20 min at 40% and 75% of maximal O2 uptake, respectively). Mean VO2 max at HA was 27% lower than at SL. Resting plasma levels of aldosterone (Aldo), renin, and angiotensin II (A II) were significantly lower (P smaller than 0.05) on day 1 at HA compared to SL, but returned to SL values by day 11. Plasma cortisol values at rest were similar at SL and HA and were not significantly altered by light or moderate exercise. Renin, A II, and Aldo rose progressively with increasing workload in each environment. With acute HA, renin and Aldo were lower than at either SL or chronic HA. The chronic HA levels tended to approximate SL findings, implying adaptation. The data suggest that aldosterone is predominantly under the control of the renin-angiotensin system during graded exercise at sea level and that the response of this system is altered on acute high-altitude exposure.

Testosterone metabolism in benign and malignant breast lesions.

Abstract: Tissues from a variety of breast lesions were incubated with 14C-testosterone (17beta-hydroxy-4-androsten-3-one). Conversion to 14C-5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) and 14C-androstenedione (4-androsten-3,17-dione) was measured. Normal breast tissue showed formation of 14C-androstenedione but no formation of 14C-5alpha-dihydrotestosterone. Fibroadenomas showed a high degree of testosterone metabolism forming both 14C-androstenedione and 14C-5alpha-dihydrotestosterone. The adenocarcinomas of the breast, contrary to a previous report in the literature, showed no conversion to 14C-5alpha-dihydrotestosterone. The data suggest that formation of 5alpha-dihydrotestosterone is a predominant metabolic pathway in fibroadenoma.