Tissues from a range of fish were examined for the presence of
parathyroid hormone-related protein (
PTHrP) to investigate
PTHrP protein distribution and
PTHrP gene expression in jawless fish, cartilaginous fish, and bony fish. Immunoreactive
PTHrP was localized using
antisera to N-terminal and mid-molecule regions of human
PTHrP and
PTHrP gene expression examined using a
digoxigenin labeled riboprobe to a conserved region of the mammalian
PTHrP gene. In all of the fish studied,
PTHrP protein and
messenger RNA (
mRNA) were localized to the skin, kidney, and skeletal muscle, following the pattern seen in higher vertebrates. Additional sites of localization for both
protein and
mRNA included gill, nerve cord, and pituitary, as well as developing 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 higher vertebrates. The results imply that the distribution of
PTHrP is widespread in fish and that there is homology between the
PTHrP molecules found in 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. J. Exp. Zool. 284:541-548, 1999.