[Bovine epiphyseal lactotropin, biologically and immunochemically related to pituitary prolactin].

A substance biologically and immunologically related to the hypophysis lactogenic hormone (HLH) was detected in a purified preparation obtained by extracting the bovine pineal glands (epiphyses) with acidified acetonic saline fractionation, precipitation in isoelectric point and gel filtration. Bioactivity of the pineal gland lactogen was evaluated according to its ability for stimulating the pigeon thyroid gland proliferation. Equal doses of the pineal gland hormone and HLH produced the same biological effect. The lactogen immunochemical properties were studied by gel precipitation in agar gel, immunoelectrophoresis and radioimmunoconcurrent technique. Absolute identity of the hormone immunochemical properties was revealed. Molecular weights of both lactogens, determined by chromatography on Sefadex C-75, were equal. The average HLH content in the organ, determined by radioimmunochemistry, was 4.7 X 10(5) micrograms for the hypophysis and 9.6 X 10(2) micrograms for the pineal gland. HLH content, calculated per 1 mg protein, was 3 X 10(3) micrograms for the hypophysis and 24 micrograms for the pineal gland. The hormone content in the epiphysis was 1000 times higher than HLH concentration in the blood serum.