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Biomedical subjects

P J Drew

Publications and source records attributed to P J Drew.

6 recordsLinked to original sources
PubMed1988

Role of the adrenal cortex in the natriuresis associated with vasopressin infusion.

We have compared the effects of a 48-h continuous infusion of arginine vasopressin (AVP) given to four subjects (one subject studied twice) with that given to four patients lacking adrenocortical function and maintained on fixed doses of mineralocorticoid and glucocorticoid replacement therapy. Both patients and normal subjects were subjected to dietary salt and water restriction during the period of the infusion, and all participants were in balance on a low sodium diet at the start of the infusion period. Infusion of vasopressin in normal subjects was associated with an increase in fractional excretion of sodium by the kidney, which continued during the day after the infusion was stopped. The infusion was also associated with a fall in plasma aldosterone as well as falls in whole blood packed cell volume, plasma renin activity and plasma noradrenaline. Infusion of vasopressin in patients lacking adrenocortical function was associated with a smaller increase in fractional excretion of sodium by the kidney in comparison with that seen in normal subjects, and the increase in sodium excretion was confined to the period of the infusion. Mineralocorticoid activity was maintained constant during the infusion, although a fall in whole blood packed cell volume, plasma renin activity and plasma noradrenaline were noted, in similarity to the study made in normal subjects. We conclude that changes in mineralocorticoid activity are the main factors contributing to the increase in renal sodium excretion seen during, and after, the continuous infusion of vasopressin in salt- and water-restricted man.

Adrenal Cortex↗
PubMed1985

Effect of angiotensin converting-enzyme inhibition on potassium-mediated aldosterone secretion in essential hypertension.

1. Eight patients with essential hypertension were challenged with an infusion of 32 mmol of potassium chloride in saline before and after control of their blood pressure by the angiotensin converting-enzyme (ACE) inhibitor enalapril. 2. The potassium infusion was associated with similar increases in plasma aldosterone before and during enalapril treatment, although absolute aldosterone levels were lower after enalapril treatment despite higher plasma potassium levels. 3. The handling of the potassium load was altered by ACE inhibition. The area under the curve of a plot of the increase in plasma potassium above baseline against time was greater during enalapril treatment than during treatment with placebo. 4. These observations contrast with data obtained in the dog and demonstrate that in patients with essential hypertension stimulation of aldosterone secretion by potassium is not abolished by chronic suppression of plasma angiotensin II; and although plasma aldosterone remains at a lower level, the homoeostasis of plasma potassium is only mildly impaired.

Adult↗
PubMed1985

The effect of arginine vasopressin on ureagenesis in isolated rat hepatocytes.

The effect of arginine vasopressin (AVP) on ureagenesis was measured in isolated rat hepatocytes with ammonium chloride and L(+)-lactate as substrates. AVP was found to stimulate urea synthesis and the dose-response curve suggests that such an effect is present at concentrations of the hormone as low as 25-50 pmol/l. Both the dose-response curve and the concentrations of NH+4 employed suggest that the effect observed could be of physiological significance.

Animals↗
PubMed1985

The effect of acute beta-adrenoceptor blockade on examination performance.

Simple tests of verbal reasoning and mental arithmetic, taken under mildly stressful conditions, have been shown to give a reproducible test of intellectual function within groups of normal subjects. Using these tests, in two separate examinations, a double-blind cross-over study was performed on 35 medical students to assess the effects of acute beta-adrenoceptor blockade with propranolol on intellectual function. With placebo treatment, students recorded an average total score of 231.3 marks, with average scores of 108.9 marks on the mental arithmetic paper and 122.4 marks on the verbal reasoning paper. Treatment with propranolol was associated with an improvement in total score of 9.2 +/- 3.9 marks (P less than 0.05), an improvement in mental arithmetic score of 5.6 +/- 2.3 marks (P less than 0.05) and an improvement in verbal reasoning score of 3.6 +/- 2.4 marks (NS). Eighteen out of the 35 students said that they were mildly anxious before one examination and 13 students said they were anxious before both examinations. Those students who admitted anxiety seemed to benefit the most, in terms of improved examination performance, from treatment with propranolol.

Adrenergic beta-Antagonists↗