Parathyroid hormone-related protein (PTHrP) in cartilaginous and bony fishtissues

Tissues from a range of fish were examined for the presence of parathyroid hormone-related protein (PTHrP) to investigate PTHrP protein distribution a nd PTHrP gene expression in jawless fish, cartilaginous fish, and bony fish . Immunoreactive PTHrP was localized using antisera to N-terminal and mid-m olecule regions of human PTHrP and PTHrP gene expression examined using a d igoxigenin labeled riboprobe to a conserved region of the mammalian PTHrP g ene. In all of the fish studied, PTHrP protein and messenger RNA (mRNA) wer e localized to the skin, kidney, and skeletal muscle, following the pattern seen in higher vertebrates. Additional sites of localization for both prot ein and mRNA included gill, nerve cord, and pituitary, as well as developin g dermal denticles and rectal gland in the elasmobranch species. The sites of PTHrP distribution indicate that PTHrP may have roles in ionoregulation as well as growth and differentiation in fish, as has been suggested in hig her vertebrates. The results imply that the distribution of PTHrP is widesp read in fish and that there is homology between the PTHrP molecules found i n humans and fish. The conservation of localization and possible similarity of the PTHrP molecules between tetrapods and fish suggests that PTHrP has a number of fundamental roles in vertebrates. (C) 1999 Wiley-Liss, Inc.