Transepithelial electrophysiology of cultured mouse mammary epithelium: sensitivity to prolactins.

Several prolactins and growth hormones affect cultured BALB/c mouse mammary epithelial electrophysiology at doses of 10 micrograms/ml. Ovine prolactin is effective at doses as low as 1 ng/ml, levels that are three to four orders of magnitude less than effective amounts of rat growth hormone. Because growth hormone preparations may have approximately 1% prolactin contamination, its effects are probably due to prolactin contamination. The maximum effect of ovine prolactin on short-circuit current and on resistance occurs at doses differing by two orders of magnitude, indicating that these two effects of prolactin may be partially separable. Therefore, prolactin may have effects on passive permeability properties in addition to its documented effects on active transport.