Environmental Calcium and the Sensitivity of Killifish(Fundulus heteroclitus) in Bioassays for the HypocalcemicResponse to Stannius Corpuscles from Killifish andCod (Gadus morhua)

Abstract

The hypocalcemic response of killifish, Fundulus heteroclitus, to Stannius corpuscle homogenates was significantly increased by adapting the fish to a low-calcium environment. A simple bioassay for the hypocalcemic substance was developed. Killifish were adapted to calcium deficient sea water and fed low calcium food for at least six weeks. They were given 4 daily injections of tissue homogenates and serum calcium levels were determined two hours after the final injection. Both cod (Gadus morhua) and killifish Stannius corpuscle homogenates produced significant hypocalcemia. The responses were log-dose related. Liver and kidney homogenates had no effect. Cortisol, angiotensin amide and salmon calcitonin did not elicit hypocalcemia in the present assay system. The name “hypocalcin” was proposed for the hypocalcemic factor(s) in this tissue. (Endocrinology94: 548, 1974)