[The effect of acute administration of ketanserin on the peripheral metabolism of serotonin and hemodynamic indicators in hypertensive patients].

The effect of IV administration of ketanserin (Janssen Pharmaceutica, Beerse, Belgium) on peripheral serotonin (5HT) metabolism and on hemodynamic parameters was compared with the placebo effect. Ten hypertensive patients were infused placebo (400 ml of 5% glucose) or received 20 mg ketanserin IV followed by infusion of 20 mg ketanserin in 400 ml of 5% glucose. Increase in platelet 5HT consent without changes in plasma 5HT plasma levels, increase in urinary 5HT excretion and decrease in 5-hydroxyindole-acetic acid (5HIAA) excretion were observed under ketanserin administration compared to the placebo period. Blood pressure dropped effectively under ketanserin. Total peripheral resistance (TPR) decreased markedly in 2 patients with high initial TPR values. No changes in circulating volume, hematocrit and diuresis were observed. No correlation was found between the parameters of peripheral 5HT metabolism and water metabolism. The decrease in urinary 5HIAA excretion reflected presumably the decreased platelet turnover. The increase in urinary 5HT excretion may have resulted from increased 5HT availability for the proximal tubular cell transport system of organic cations or it may have been the consequence of altered renal 5HT metabolism caused by ketanserin. The concurrent increase in platelet 5HT content and decrease in platelet aggregation indicates a stabilizing effect of ketanserin on hyperactive platelets in hypertensive patients. The effect of ketanserin on platelet turnover is presumably involved in the mechanism of its antihypertensive and antiaggregatory action.