1. A symptomatic diuresis, polyuria, sometimes accompanies paroxysmal tachycardias in man. A study was undertaken in patients with inducible supraventricular tachycardia, irrespective of the symptom of polyuria, to measure simultaneous changes in urine output and plasma hormone levels during the arrhythmia. 2. During 14 episodes of induced tachycardia in 10 patients, there was a significant increase in mean urine flow, which was independent of the state of patient hydration. During a mean tachycardia duration of 30 ± 3 min, the mean group urine flow increased from 3.2 ± 2.3 ml/min to 7.6 ± 3.7 ml/min ( P <0.001). This was characterized by a consistent increase in free water excretion and a variable increase in sodium excretion. 3. The plasma atrial natriuretic peptide level (five patients) significantly increased from 7.6 ± 4.6 pg/ml to 34.6 ± 21.7 pg/ml ( P <0.02) during the arrhythmia. There was no significant change in the plasma argininevasopressin level and a non-significant reduction in plasma renin activity. 4. This study has shown that induced supraventricular tachycardias in man are accompanied by a significant diuresis. The mechanisms responsible remain unknown, but do not appear to involve the plasma arginine-vaso-pressin level alone.

1. A dynamic column superfusion system has been developed for the study of renin secretion in rat renal cortical cells. 2. Cells were isolated by collagenase digestion and mechanical dispersion, before suspension with polyacrylamide beads and superfusion with oxygenated physiological medium. 3. Renin was detected in the superfusate by incubation of fractions with excess nephrectomized sheep substrate in the presence of angiotensinase inhibitors followed by radioimmunoassay of the angiotensin I generated. 4. Optimized methodology included a purposebuilt polytetrafluorethylene flow cell, a 1 h equilibration to achieve a steady state, 5 min eluate collections, a 15 min stimulatory and a 30 min recovery period, and duration of perfusion of up to 270 min. 5. Significant increments above baseline renin release were seen with the stimuli of adrenaline, noradrenaline and isoprenaline. These could be demonstrated with concentrations of 10 −9 mol/l (adrenaline), 5 × 1O −10 mol/l (noradrenaline) and 1O −9 mol/l (isoprenaline). 6. This technique has significant advantages over previous methods for the study of renin secretion in vitro at the cellular level. It is reproducible and sensitive, and avoids many of the limitations of static cell suspension and kidney slice methods.

1. Opioid involvement in the physiological and hormonal responses to acute exercise was investigated in six normal male subjects. Each was exercised to 40% (mild exercise) and 80% (severe exercise) of his previously determined maximal oxygen consumption on two occasions, with and without an infusion of high-dose naloxone. The exercise task was a bicycle ergometer; mild and severe exercise were performed for 20 min each, followed by a recovery period. 2. Exercise produced the expected increases in heart rate, blood pressure, ventilation, tidal volume, respiratory rate, oxygen consumption and carbon dioxide production. After severe exercise, naloxone infusion increased ventilation from 94.8 ± 4.9 litres/min to 105.7 ± 5.0 litres/min ( P <0.05), but had no effect on any of the other physiological variables. 3. Exercise-induced changes in several hormones and metabolites were noted, including elevations in circulating lactate, growth hormone (GH), prolactin, cortisol, luteinizing hormone (LH), follicle stimulating hormone (FSH), adrenaline, noradrenaline, plasma renin activity (PRA) and aldosterone. There was no change in plasma met-enkephalin. Naloxone infusion produced the expected increases in LH and cortisol, but also significantly enhanced the elevations in prolactin, adrenaline, noradrenaline, plasma renin activity and aldosterone ( P <0.05). 4. Psychological questionnaires revealed minor mood changes after exercise, but no evidence was found for the suggested ‘high’ or euphoria of exercise. Effort was perceived as greater during the naloxone infusion than the saline infusion in every subject. 5. We conclude that endogenous opioids may be important in the control of ventilation and the perception of effort at high levels of power output, and may modulate the responses of circulating catecholamines and the renin-aldosterone system to acute physical stress.