HYPOCALCEMIC AND HYPERCALCEMIC PEPTIDES IN FISH PITUITARY-GLANDS

Immunoreactive parathyroid hormone (irPTH), PTH-related peptide (PTHrp), and stanniocalcin-like peptides were detected in Coho salmon pituitary glands. The PTH, PTHrp, and stanniocalcin immunoreactivity of the salmon pituitary was separated by high-performance liquid chromatography purification into distinct peptide fractions that coeluted with pure preparations of these hormones. Stanniocalcin was localized by immunocytochemistry in the neurohypophysis and preoptic area of the platyfish brain, in areas in which irPTH has previously been detected in other teleosts. Although it is well established that the fish pituitary exerts hypercalcemic control over calcium metabolism, these results demonstrate the presence of hyper- and hypocalcemic peptides in teleost pituitary glands. The detection of PTHrp in the fish pituitary is the first report of its presence outside of mammalian species and suggests an early evolutionary divergence of PTH and PTHrp from an ancestral gene.