Stanniocalcin: a novel protein regulating calcium and phosphate transport across mammalian intestine

Abstract

Stanniocalcin (STC) is an anti-hypercalcemic glycoprotein hormone previously identified in the corpuscles of Stannius in bony fish and recently in the human genome. This study undertook to express human STC in Chinese hamster ovary (CHO) cells and to determine its effects on calcium and phosphate absorption in swine and rat intestine. Unidirectional mucosal-to-serosal (Jm-->s) and serosal-to-mucosal (Js-->m) 45Ca and 32P fluxes were measured in vitro in duodenal tissue in voltage-clamped Ussing chambers. Addition of STC (10-100 ng/ml) to the serosal surface of the duodenum resulted in a simultaneous increase in calcium Jm-->s and Js-->m fluxes, with a subsequent reduction in net calcium absorption. This was coupled with an STC-stimulated increase in phosphate absorption. Intestinal conductance was increased at the highest dose of STC (100 ng/ml) in swine tissue. The addition of STC to the mucosal surface had no effect on calcium and phosphate fluxes. STC at doses of 10-1,000 ng/ml had no effect on short-circuit current in any region of the rat intestine. In conclusion, human recombinant STC decreases the absorption of calcium and stimulates the absorption of phosphate in both swine and rat duodenum. STC is a novel regulatory protein that regulates mammalian intestinal calcium and phosphate transport.