SUMMARY1. Bio-assay techniques have been used to measure plasma levels of neurohypophysial hormones in man, following either a single injection or a continuous infusion.2. The median half-life of oxytocin after a single injection of 2 u. was 3*2 min (2-0-5*7, 95 % confidence limits); this increased significantly (P < 0*01) to 4-8 min (4-4-6-1) when the hormone was infused at a rate of 500 m-u./min. The vasopressins had appreciably longer half-lives. After a single injection of 1 or 1-5 u. 8-lysine vasopressin (LVP), the half-life was 5*7 min (3.6-6-0). Continuous infusions of the hormones at a rate of 120 m-u./min yielded half-lives of 5-5 min (5.0-7-1) for LVP, and 5-6 min (3.9-9.5) for 8-arginine vasopressin (AVP).3. The apparent volumes of distribution of the hormones were all of the order of two thirds the extracellular volume.4. In accordance with its shorter half-life, the clearance of oxytocin was greater than that of the vasopressins (1.5 1./min, compared with 1.0 I./ min). 5. The antidiuretic potencies of the hormones were studied in overhydrated subjects, by measuring the rate of urine excretion following an i.v. injection. Duration of antidiuretic action increased in the order: oxytocin, LVP, AVP. A 5: 1 mixture of oxytocin and AVP was not as longlasting as AVP alone. 8-5 % (4-22) of an administered dose of AVP was excreted in the urine, and this amount was significantly correlated with urine volume (r = + 0-67, P < 0.05). MIRIAM FABIAN AND OTHERS 6. Ultrafiltration of human plasma containing exogenous hormones showed that 30 % (13-50) of AVP was bound, the degree of binding being independent of concentration over the range used (50-400,-u./ml.) In contrast, oxytocin was completely unbound.7. Exogenous oxytocin was more stable than exogenous AVP in human plasma. At 40 C there was no significant loss of oxytocin until 7 days, whereas 20 % of AVP was inactivated in 2 days. At 370 C a 20 % loss of AVP occurred within 4 hr, and a 50 % loss within 24 hr; corresponding times for oxytocin were 24 and 48 hr.

SummaryThree patients suffering from non-puerperal galactorrhoea over periods ranging from two months to six years were treated with an ergot alkaloid, 2-Br-alphaergocryptine (CB 154). In all three cases the galactorrhoea was terminated. The apparent prolactin antagonism exhibited by this compound is discussed.

SummaryA double-blind trial was performed in 60 women to establish the effectiveness of an ergot alkaloid, 2-Bralpha-ergocryptine (ergocryptine; CB 154), in suppressing puerperal lactation and to compare it with stilboestrol and a placebo. At the doses selected ergocryptine and stilboestrol were equallyeffective.

A double blind trial of bromocriptine in the treatment of 14 patients with the symptoms of benign prostatic hypertrophy is reported. 5 patients did not complete the trial mainly because of side-effects due to an overdosage of bromocriptine. In the remaining 9 patients there was symptomatic improvement in 6, with objective evidence of improvement in 3 patients on flow rate measurements. The possible modes of action of bromocriptine in this condition are discussed.

Proton nuclear magnetic resonance ('H NMR) has been used to measure rapidly concentrations of metabolites in plasma from patients with chronic renal failure (CRF) and normal subjects. Detailed quantitative analyses of spectra are presented for four CRF patients during haemodialysis, two patients in early stages of renal failure and two normal subjects. For patients on acetate dialysis, the method clearly shows how well exogenous acetate is metabolized during and after dialysis. Our results indicate a discrepancy between creatinine concentrations measured by 'H NMR and by the kinetic Jaff6 reaction method, and also point to high betaine concentrations in plasma from some patients on maintenance haemodialysis and taking folate supplement.