Effects of water temperature and salinity on parathyroid hormone-related protein in the circulation and tissues of elasmobranchs

Parathyroid hormone-related protein (PTHrP) is a hypercalcemic factor in ma mmals. The PTHrP antigen has been localized in both bony and cartilaginous fish tissues. Sites of localization included gills, skin and kidney, organs involved in osmoregulation. Physiological and localization experiments wer e carried out in elasmobranchs to dissect PTHrP's possible role in osmoregu lation. The effects of alterations in the external environment on PTHrP in sharks were examined by keeping juvenile animals under conditions of increa sed temperature or decreased salinity. There were no alterations in the PTH rP levels in either the circulation or tissues. Significant correlations be tween plasma PTHrP, electrolyte and urea levels were seen in the pretreatme nt samples. The localization of PTHrP by immunohistochemistry and in situ h ybridization revealed conserved sites of distribution from elasmobranchs to mammals, including skin, kidney, muscle and skeleton. (C) 2001 Elsevier Sc ience Inc. All rights reserved.