Serotonin metabolism and platelet aggregation under antihypertensive treatment with nitrendipine.

The effect of antihypertensive treatment with nitrendipine (10-40 mg/day) on serotonin metabolism and platelet aggregation was investigated in 13 hypertensive patients over a 6-month period. Normalization of elevated blood pressure was achieved [systolic blood pressure (SBP): 167 +/- 4 to 148 +/- 4 mm Hg, p less than 0.01; diastolic blood pressure (DBP): 108 +/- 2 to 95 +/- 3 mm Hg, p less than 0.01; chi +/- SEM before and after the treatment]. The decrease in plasma serotonin (5-HT) levels (354 +/- 140 to 179 +/- 49 nmol/L) and the platelet 5-HT content (9.6 +/- 3.5 to 2.8 +/- 0.9 nmol/10(9) Tro) was observed. Urinary 5-HT and 5-hydroxyindolacetic acid output did not show significant changes. Although the platelet aggregation decreased only moderately, a positive correlation was found between the 5-HT levels in platelet-poor plasma and platelet aggregation indices I (r = 0.699; p less than 0.001). The impaired 5-HT metabolism parameters (high platelet serotonin content and low 5-HT urinary output) in a washout period were normalized under the treatment with nitrendipine. It is concluded that the interaction with serotonergic metabolism could participate in antihypertensive mechanisms of nitrendipine. This effect is of clinical and theoretical importance when taking into account 5-HT atherogenic and mitogenic activity.