EFFECTS OF OVINE PROLACTIN, BOVINE GROWTH-HORMONE AND TRIIODOTHYRONINE ON THE CALCIFICATION OF OTOLITHS AND SCALES IN THE HYPOPHYSECTOMIZEDGOLDFISH CARASSIUS-AURATUS

The involvement of ovine prolactin (oPRL), bovine growth hormone (bGH) , and triiodothyronine (T-3) in otolith and scale calcification was ex amined using hypophysectomized goldfish Carassius auratus. Hypophysect omized fish received three intraperitoneal injections of either oPRL, bGH, or T-3 every other day, and were kept in water containing Ca-45 d uring the last 3 days. Otoliths (asterisci) and scales were dissected and the rate of calcium incorporation into these tissues was determine d. Plasma calcium and sodium concentrations were also measured. Hypoph ysectomy resulted in hypocalcemia and hyponatremia, which were correct ed by oPRL replacement therapy. T-3 was effective in correcting only t he hypocalcemia. Therapy with bGH induced a further reduction in plasm a calcium concentrations below the level of the hypophysectomized cont rol. Calcium incorporation into otoliths and scales was also markedly reduced after hypophysectomy. oPRL was ineffective in stopping this re duction. T-3 corrected the reduction in scales, but not in otoliths. T herapy with bGH completely counteracted the reduction in otoliths and scales and even exceeded the respective sham levels. These results sug gest that pituitary hormones, particularly GH, are relevant to otolith and scale calcification, possibly via matrix-related sequences.