Influence of alpha-tocopherol on prostacyclin synthesis by rat's arterial and myometrial tissues

Influence of alpha-tocopherol on PGI2 synthesis by rat arterial and myometrial tissues was investigated using a rat platelet antiaggregatory bioassay. Chronic administration of alpha-tocopherol to female rats (10 mg kg-1 day-1 s.c. for 14 days) significantly increased ex-vivo PGI2 synthesis by the arterial tissue from 12.7 +/- 0.3 (control, mean +/- s.e.m) to 17.2 +/- 0.4 ng PGI2 mg-1 wet tissue and by the myometrial tissue (in proestrus) from 1.1 +/- 0.07 (control) to 1.85 +/- 0.1 ng PGI2 mg-1 wet tissue (P less than 0.05, n = 6). alpha-tocopherol (5 mg kg-1 day-1 for 14 days) did not stimulate PGI2 to any significant level. Pretreatment of male rat arterial tissue with alpha-tocopherol (0.02, 0.1 or 0.2 mM) in vitro increased PGI2 synthesis in a dose-dependent manner. At a dose of 0.2 mM it increased PGI2 synthesis from 13.70 +/- 0.70 (control) to 22.6 +/- 1.4 ng PGI2 mg-1 wet tissue (P less than 0.1, n = 6). Pre-treatment of 14-day pregnant rat myometrium with alpha-tocopherol 0.2 and 0.4 mM significantly increased PGI2 synthesis from 1.2 +/- 0.06 (control) to 1.90 +/- 0.12 and 2.1 +/- 0.1 ng PGI2 mg-1 wet tissue, respectively (P less than 0.05, n = 6). The results indicate that the ability of alpha-tocopherol to stimulate PGI2 synthesis may partly contribute towards better understanding of the mechanisms that underly the protective effect of alpha-tocopherol against experimentally induced decreases in coronary flow and intravascular coagulations in some mammals. Furthermore adequate intake of alpha-tocopherol during pregnancy may enhance uterine blood flow and ensure adequate foetal nutrition.