Effect of prolactin administration on ovarian and thyroidal activity in relation to gonadotropic and thyrotropic potency in a freshwater catfish, Heteropneustes fossilis (Bloch).

Radiophosphorus incorporation by ovary was the criterion used for the assessment of ovarian activity in H. fossilis. Prolactin administration at different dose levels failed to elicit any obvious change in ovarian 32P uptake. From the findings of this experiment it appears that prolactin has no influence on ovarian activity. However, it exerted an inhibitory effect on the thyroid activity in intact H. fossilis. It was evident by retarded thyroidal 131I uptake. But the declension in serum PB131I was less pronounced. TSH content of the pituitary gland in response to prolactin administration was also reduced. It seems that prolactin interferes in thyroidal iodine accumulation perhaps by retarding the synthesis of TSH, but apparently does not prevent thyroxine output to a perceptible level.