LONG-TERM TREATMENT OF MODERATE HYPERTENSION WITH PENBUTOLOL (HOE893D) .2. EFFECT ON RESPONSE OF PLASMA CATECHOLAMINES AND PLASMA-RENIN ACTIVITY TO INSULIN-INDUCED HYPOGLYCEMIA

The effect of insulin-induced hypoglycemia on the blood levels of catecholamines and renin activity was studied in 5 patients with moderate hypertension before and after treatment for 3-8 mo. with penbutolol (PEN) 20-30 mg twice daily. Penbutolol caused no change in fasting blood glucose level. Insulin 0.1 IU per kg body wt i.v. reduced blood glucose concentration by approximately 50% after 30-45 min, both before and during treatment with penbutolol. Hypoglycemia prior to medication was accompanied by a marked increase in the production of adrenaline and a minor increase of noradrenaline in all 5 patients. During treatment the response of adrenaline to hypoglycemia was reduced in 4 patients and the data was inconclusive in one. Basal renin activity was rather low in 3 patients, within the normal range in 1 and relatively high in 1. Before penbutolol the hypoglycemia-induced increase in catecholamine production caused no change in plasma renin activity in the 3 patients with low basal levels, whereas a marked increase was observed in the other 2. During medication plasma renin activity remained unchanged on induction of hypoglycemia regardless of the catecholamine response. Despite the marked increase in plasma adrenaline following insulin-induced hypoglycemia, no statistically significant increase in pulse rate was recorded.