Lack of Specificity for the Extra-Ovarian Prolactin Effect on Vaginal Mucification in Rats1

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Abstract
In order to determine if an extraovarian vaginal mucification response to prolactin could be used as a mammalian bioassay for prolactin, a series of experiments was performed in which the specificity of the response was studied. The effects of bovine and ovine growth hormone, adrenocorticotropic hormone (ACTH) and human placental lactogen (hPL) on vaginal mucification, as quantified by measuring vaginal sialic acid concentration in hypophysectomized-ovariectomized rats treated with estrogen and progesterone, were examined. Growth hormone and prolactin had additive effects on vaginal sialic acid concentration, even when prolactin was given in amounts which, in the absence of other pituitary hormones, maximally stimulated vaginal sialic acid concentration. This suggests that growth hormone has a different action on the vagina to that of prolactin. Both estrogen and progesterone were necessary for the growth hormone effect. A dose of ACTH which doubled adrenal weights did not have a significant effect on vaginal sialic acid concentration. hPL significantly increased vaginal sialic and concentration. Its effect was not additive to that of prolactin, suggesting that the site of action of hPL is the same as that for prolactin. It was concluded that, because of lack of specificity, vaginal mucification has limited usefulness as a mammalian bioassay for prolactin. (Endocrinology92: 847, 1973)

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