Effect of quinapril therapy on blood pressure and serotonin change in patients with mild to moderate hypertension.
BACKGROUND
Previous studies have shown that serotonin plays an important role in hypertension because of its vasoconstrictive effect, mediated through serotonergic receptors. Angiotensin-II is a potent vasopressor which facilitates the aggregation of platelets, subsequently releases serotonin. Because quinapril is an angiotensin-converting enzyme inhibitor and could result in a decrease of angiotensin-II, Quinapril was used to treat patients with mild or moderate hypertension in order to observe the change of plasma serotonin.


METHODS
Twenty-two patients, (10 males, 12 females, mean age 45 yrs) without other major medical diseases and secondary causes of hypertension, were selected for this study. High performance liquid chromatography (HPLC) with electrochemical detection was used to detect the plasma serotonin. These patients were given placebos for two weeks before the first dose of quinapril (5 mg). Thereafter, the dosage was adjusted according to the response of blood pressure to a desired value (BP < 140/90 mmHg). At about 14:00 hours on the first day, after the patient had rested for an hour and was in a quiet condition, blood was drawn by venipuncture with heparin as anti coagulant; the plasma serotonin concentration was determined for the baseline value. The plasma serotonin level was rechecked eight weeks later.


RESULTS
It was found that systolic blood pressure began to decrease significantly two weeks after quinapril therapy, and then reached a constant state. Blood pressure decreased from 174/107 mmHg to 134/87 mmHg. Among these 22 patients, there were 14 (65%) whose blood pressure reduced to a normal range. Plasma serotonin also decreased significantly from 4.69 +/- /3.67 ng/ ml to 2.89 +/-2.64 ng/ml (p < 0.05). According to this data, 15 in 22 patients (68%) had reduction of plasma serotonin. There was little correlation between change in blood pressure and change of plasma serotonin; the correlation co-efficiency is only 0.019.


CONCLUSIONS
This study shows that quinapril has an antihypertensive property and serotonin-lowering effect. Since there was no correlation between the change of serotonin and blood pressure, these two actions of quinapril might have been mediated through different mechanisms.
Huang
J L
JL
Department of Medicine, Taichung Veterans General Hospital, Taipei, Taiwan, R.O.C.
Cheng
F C
FC
Chen
Y T
YT
Ting
C T
CT
D000328:Adult; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D007546:Isoquinolines / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D000077583:Quinapril; D012701:Serotonin / Q000097:blood*; D044005:Tetrahydroisoquinolines
D000959:Antihypertensive Agents; D007546:Isoquinolines; D044005:Tetrahydroisoquinolines; D012701:Serotonin; D000077583:Quinapril