Does calcium channel blockade and beta-adrenergic blockade affect platelet function and fibrinolysis to a varying degree?
The effects of isradipine and atenolol on platelet function and fibrinolytic activity were studied in 10 male patients with mild untreated hypertension. After a 2-week placebo run-in period, the volunteers were randomized to either isradipine 2.5 mg twice daily or atenolol 100 mg daily for a 6-month period. Those initially receiving isradipine then received atenolol and vice versa. After each therapy regimen, blood was drawn at rest and 1 h after exercise during a maximum exercise test. Platelet activity in vivo was estimated as release of B-TG and PF-4. Fibrinolytic activity was estimated as the fast-acting inhibitor against tissue plasminogen activator usually termed PAI-1. During atenolol and isradipine therapy, blood pressure (BP) was equally reduced (p < 0.05). Heart rate (HR) decreased during atenolol treatment but was not changed by isradipine. Platelet activity in vivo estimated as B-TG and PF-4 decreased irrespective of therapy (p < 0.02). During atenolol, as during placebo therapy, exercise resulted in a significant increase in platelet activity, as shown by an increase in B-TG (p < 0.02) and in PF-4 (p < 0.01). Such increase was not observed during isradipine treatment. Both treatments tended to improve fibrinolysis, as shown by a decrease in PAI, 1 h after exercise. Reducing BP with isradipine or atenolol results in a similar decrease in platelet activity and PAI-level, tested at rest and 1 h after rest, respectively. During exercise, platelet activity increased during atenolol treatment; such change did not occur during isradipine treatment.
Gleerup
G
G
Department of Clinical Physiology, Fredericksberg Hospital, Denmark.
Mehlsen
J
J
Winther
K
K
D000328:Adult; D000368:Aged; D001262:Atenolol / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015444:Exercise; D005260:Female; D005342:Fibrinolysis / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000188:drug therapy*; D017275:Isradipine / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects; D011863:Radioimmunoassay; D001620:beta-Thromboglobulin / Q000378:metabolism
D017395:Plasminogen Activator Inhibitor 1; D001620:beta-Thromboglobulin; D001262:Atenolol; D017275:Isradipine