PROLACTIN-LIKE ACTIVITY IN THE PITUITARY GLAND OF THE FROG

Abstract

SUMMARY Homogenates of the distal lobe and combined intermediate and neural lobes from Rana temporaria and R. esculenta and extracts of these lobes, purified by zone electrophoresis in starch gel or by Sephadex column chromatography, were tested for crop-stimulating activity in the pigeon and lactogenic activity in the rabbit. The response of the pigeon crop to injections of homogenates resembled the reaction produced by purified sheep prolactin, but differed in intensity and in the number of fatty 'granules' present. The response in the rabbit differed considerably from the reaction to sheep prolactin. Milk was absent in spite of extensive proliferation in the gland. Injections of purified fractions of the pituitary extracts yielded similar results. It is concluded that a prolactin-like principle is present in the frog pituitary in both the distal lobe and the combined intermediate and neural lobes which can initiate a prolactin-like response in both the pigeon and the rabbit but cannot bring about the completion of a typical prolactin reaction.