SOMATOSTATIN AND OXYTOCIN INFUSION INHIBITS THE RISE OF PLASMA β‐ENDORPHIN, β‐LIPOTROPHIN AND CORTISOL INDUCED BY INSULIN HYPOGLYCAEMIA

The present study investigated the possible effect of somatostatin and oxytocin on the basal and stress‐induced rise of beta‐endorphin (β‐END), beta‐lipotrophin (β‐LPH) and cortisol in the human. For this purpose somatostatin (4.1 μg/min for 120 min or oxytocin (0·4 μg/min for 120 min) was infused into two different groups of seven healthy subjects; 30 min after the start of the infusion, placebo or insulin (0·1 IU/kg body weight, B.W.) was injected on two different days. In a third experimental step, an insulin tolerance test was performed during saline infusion to evaluate stress‐related effects on the different hormonal secretions under basal conditions. Plasma levels of β‐END, β‐LPH and cortisol were measured by radioimmunoassay. Extraction and chromatographic procedures preceded the assay for β‐END and β‐LPH. Neither somatostatin nor oxytocin significantly modified basal plasma levels of β‐END, β‐LPH and cortisol. However these treatments blunted the rise of the three hormones seen at 45 and 60 min during insulin‐induced hypoglycaemia (P> 0·01). These results indicate that somatostatin and oxytocin may influence the β‐END, β‐LPH and cortisol increase induced by stress in humans, without affecting their basal secretion.