ASSAYS FOR GONADOTROPHINS IN THE PITUITARY GLAND OF THE ARCTIC COD, GADUS MORHUA L., AND THE PRESENCE OF A GONADOTROPHIC ANTAGONIST

Abstract

SUMMARY: The presence of gonadotrophins in the pituitary gland of the cod was demonstrated in assays on other lower vertebrates. Injections of cod pituitary stimulated a 42% increase in the ovarian weight of the female rudd (Scardinius erythrophthalmus L.), and sperm release in the male common frog (Rana temporaria). The injection of cod pituitary powder into immature rats failed to cause any increase in ovarian weight in standard assays. In all experiments the resulting ovarian weights of the treated animals were slightly less than those of the control groups. The cod pituitary also failed to induce ovulation in the mature female rabbit. When immature female rats were treated simultaneously with cod pituitary and with mammalian gonadotrophins, the cod pituitary inhibited the ovarian response to the mammalian hormones. This inhibition was proportional to the dose of cod pituitary given. The cod gonadotrophic antagonist was shown to be confined to the pituitary gland; injections of cod muscle powder and cod brain powder did not have any inhibitory effects. All the cod pituitary samples tested contained the antigonadotrophic factor, but there was some seasonal variation in the intensity of the inhibition produced. The nature of the cod pituitary factor is discussed, together with the significance of these results to the concept of the species specificity of vertebrate gonadotrophins.