Introduction Stanniocalcins (Stcs) are evolutionarily conserved glycoproteins. The first Stc protein was discovered from the Corpuscles of Stannius (CS), an endocrine organ unique to bony fish (1, 2). Surgical removal of CS resulted in elevated blood calcium levels and the appearance of kidney stones (3–5). Injection of CS extracts or purified Stc1 reversed these effects (6). In cultured rainbow trout CSs, secretion of Stc1 was found to be regulated by external Ca2+ levels ([Ca2+]) (6).
