Effect of Synthetic Salmon Calcitonin on Tissue Calcium Levels in the Bagrid Catfish, Mystus Gulio (Hamilton)

Effect of synthetic salmon calcitonin (SCT) on tissue calcium (Ca) level was studied in euryhallne catfish Mystus gulio. Intraperitoneal administration of 20, 40 and 60 i.u. of SCT/fish/day for 5 days produced transient but significant hypocalcemic responses in blood, ovary and air bladder. The hypocalcemia was sustained for about 24 hours post injection and the animals regained normocalcemia in about 48 hours. During the same period, transient but significant hypercalcemic responses were observed in the bone and muscle of SCT treated fish that regained normocalcemia. The hypocalcemic or hypercalcemic response in the respective tissues was found to be dose dependent. The air-bladder was found to be a significant store house/supply centre for Ca and showed marked bleaching due to Ca discharge/erosion on prolonged calcitonin treatment. The same was reflected in the Ca content. The above results obtained in Mystus gulio suggest that the Ca homeostasis is efficient in this species and that calcitonin acts not only on bones but also on tissues like muscles, ovary and air-bladder.