The local effects of topically applied estradiol, cyproterone acetate, and ethanol on sebaceous secretion in intact male rats.

Estradiol in ethanol was applied once daily to one flank of intact male rats and sebum production on both flanks was measured over periods of 18 h alternating with 6 h by absorbing the lipid on pads of cigarette paper held in place by a harness, starting on the 15th day. Sebum production was very significantly less on the treated flanks than on the contralateral flanks that received only vehicle, indicating an unequivocal local effect of the estradiol. At the same time, the values on the contralateral flanks were significantly below those of littermate rats which received vehicle only, indicating that the estrogen had been systemically absorbed to produce a distal action. The estradiol also significantly reduced plasma testosterone and the relative weights of the seminal vesicles, ventral prostate, and preputial glands, which demonstrated that part of the general action of the estrogen could have been by suppression of endogenous androgen production. In short-term experiments, in which measurements were started concurrently with treatment, the inhibitory action of estradiol, in contrast to that of cyproterone acetate, was not detected until the 4th day. Indeed, it appeared probable that the estrogen actually stimulated sebum secretion over the first 2 days, suggesting that it had a biphasic effect.