IN-VITRO MODULATION OF PRIMATE CORONARY VASCULAR MUSCLE-CELL REACTIVITY BY OVARIAN-STEROID HORMONES

Susceptibility to drug-induced coronary vasospasm in rhesus monkeys in creases after removal of the ovaries and can be normalized by adding b ack physiological levels of estradiol-17 beta (E-2) and/or natural pro gesterone (P) in vivo as reported recently by our group. Furthermore, the reactivity status (Ca2+ and protein kinase C responses) of freshly isolated and primary culture coronary artery vascular muscle cells (V MC) mimic the intact coronary artery responses to 5-HT + U46619. Since coronary reactivity is maintained in the isolated VMC, we hypothesize d that the reactivity state inherent in the VMC was modulated directly by ovarian steroids in vitro as in the whole animal. To test this hyp othesis, we treated hyperreactive VMC from ovariectomized (ovx) mon ke ys in vitro with Ea or P and measured VMC reactivity to combined stimu lation with 5-HT and U46619, as determined by the amplitude and especi ally the duration of intracellular Ca2+ signals, as well as protein ki nase C (PKC) activation/translocation. VMC were treated for 12-96 h wi th 3-100 pg/ml E-2 (10-365 pM) and/or 0.3-3 ng/ml P (0.95-9.5 nM). Hyp erreactive responses to the combination of 5-HT and U46619 in untreate d VMC were significantly and dose-dependently reduced by treatment in vitro with physiological levels of either Ep or P for at least 24 h, B oth the early transient and late sustained increases in intracellular Ca2+ and PKC translocation were blunted, and the effects of 0.2 nM E-2 and 3.2 nM P were specifically antagonized by the receptor blockers I CI 182,780 (200 nM) and RU486 (15 nM), respectively. Antibodies to the estrogen receptor and progesterone receptor labeled nuclei in VMC, wh ich were also positively labeled by a smooth muscle myosin heavy chain monoclonal antibody. These data indicate that natural ovarian steroid s directly reduce hyperreactive 5-HT and thromboxane A(2)-stimulated C a2+ and PKC responses of coronary artery VMC from surgically menopausa l rhesus macaques, We hypothesize that vascular hyperreactivity, which may be a critical factor involved in the increased incidence of coron ary artery vasospasm and ischemic heart disease in postmenopausal wome n, can be normalized by E-2 and/or P through direct actions on coronar y artery vascular muscle cells.