A novel human cDNA highly homologous to the fish hormone stanniocalcin

Stanniocalcin is a glycoprotein hormone previously considered present only in bony fish where it is secreted by the corpuscles of Stannius, endocrine organs involved in Ca2+ homeostasis. In fish, stanniocalcin was thought to be an adaptation for Ca2+ regulation in aquatic environments, and its effects include inhibition of gill Ca2+ transport. We have obtained a human cDNA clone coding for a protein highly homologous to fish stanniocalcin. The mRNA is expressed in many human tissues, with the highest levels in ovary, prostate and thyroid. In vitro human cell culture studies show that the mRNA is positively regulated by extracellular Ca2+ in the medium. We conclude that a human protein similar to the fish hormone is expressed in multiple tissues rather than by a specialized endocrine organ.