Contrasting Effects of Diethylstilbestrol and Estradiol on Contraction of Isolated Rat Aorta

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Abstract
Diethylstilbestrol (DES, 1 .times. 10-6 M) inhibited norepinephrine (NE)-induced contractions of isolated rat aortic strips at low doses of NE in contrast to estradiol-17.beta. (1 .times. 10-5 M) which depressed the response to high doses. The degree of inhibition increased over 90 min exposure to the estrogens. Microsomes accumulated more 14C-DES per milligram protein than any other subcellular fraction of rat aorta. This accumulation process appears to be gradual requiring many minutes which may explain the gradual increase in intensity of the inhibitory effect with increased time of exposure to DES. The contrasting inhibitory effects of DES and estradiol in rat aorta may be due to non-homogeneous solution of these drugs in smooth muscle plasma membranes. DES, but not estradiol, caused contraction of isolated aortic strips prior to the onset of inhibition. This contraction showed fade and tachyphylaxis, was antagonized by .alpha.-adrenergic blockers, and was enhanced by prior treatment of the strips with NE. DES, but not estradiol is capable of mobilizing NE from storage sites in rat aorta.