OCCURRENCE OF MAMMOTROPHIC ACTIVITY (PROLACTIN) IN THE VERTEBRATE ADENOHYPOPHYSIS

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Abstract
SUMMARY The mammotrophic activities of the hypophysis of two teleostean species (Tilapia mossambica and Carassius auratus auratus), the African lungfish (Protopterus aethiopicus), a salamander (Necturus maculosus), a turtle (Pseudemys scripta elegans) and the domestic pigeon (Columba livia) were compared with those of the hypophysis of three laboratory mammals (rat, hamster and guinea-pig) and purified ovine prolactin. Medium from organ cultures of the pituitaries of these vertebrates was tested for mammotrophic activity by an organ-culture assay system using explants of mammary tissue from mid-pregnant A/Crgl mice. The tetrapod adenohypophyses were as effective in the induction of mammary secretion as the ovine prolactin. In contrast the glands of the lungfish and the two teleosts showed only slight mammotrophic influence. The results indicate that a principle possessing effective mammotrophic activity constitutes part of the 'pituitary apparatus' of all classes of tetrapods. Whether lungfish 'prolactin' is tetrapod-like (highly mammotrophic) or teleostean (minimally effective) in its action must still be considered unresolved, because only immature Protopterus were available.