Response of serum calcium to administration of 1,25-dihydroxyvitamin D3 in the freshwater carp Cyprinus carpio maintained either in artificial freshwater, calcium-rich freshwater or calcium-deficient freshwater.

Freshwater carps (Cyprinus carpio) were injected daily intraperitoneally either with vehicle (0.1 ml 95% ethanol/100 gm body wt), or 1,25(OH)2D3 (5 IU/100 gm body wt) and maintained either in artificial-freshwater, calcium-rich freshwater or calcium-deficient freshwater for 15 days. The specimens were sacrificed on day 1, 3, 5, 10 and 15 after initiation of the experiment and serum calcium levels were analysed. (i) Artificial freshwater: Serum calcium level of 1,25(OH)2D3 treated specimens increases progressively from day 3 to day 5. Thereafter, on day 10 and day 15 the level becomes normocalcemic. (ii) Calcium-rich freshwater: In vehicle-injected fish the serum calcium level increases progressively from day 3 to day 10. On day 15 the level becomes normocalcemic. In 1,25(OH)2D3-treated animals the serum calcium levels increase significantly from day 3 to day 5. The serum calcium level exhibits a slight fall on day 10 and day 15 although the value is still hypercalcemic. (iii) Calcium-deficient freshwater: In vehicle-injected specimens the serum calcium level shows a progressive hypocalcemia from day 3 to day 5. Thereafter the level increases thus resulting in hypercalcemia on day 15. In the 1,25(OH)2D3 treated specimens there is a significant increase in the serum calcium level from day 3 to day 10. On day 15 the level depicts a slight decrease.