IMMUNOCHEMICAL DETECTION OF PARATHYROID HORMONE-RELATED PROTEIN IN THE SACCUS VASCULOSUS OF A TELEOST FISH

Using antisera to regions of human parathyroid hormone-related protein (PTHrP) the saccus vasculosus (SV) of the sea bream (Sparus aurata) h as been shown to contain immunoreactive PTHrP. By immunohistochemistry (IHC) the epithelial coronet cells in fixed and wax-embedded SV tissu e reacted with antisera to the prepro region of human PTHrP (-13 to +2 ), the N-terminus PTHrP (1-16), and the midmolecule PTHrP (50-69). Sod ium dodecyl sulfate-polyacrylamide gel electrophoresis of saccus extra cts and incubation media contained two major proteins of 14.3 and 15 k Da. By Western blotting these two proteins both reacted with the three antisera used for IHC, suggesting that they are immunochemically simi lar to human PTHrP (1-84). Ultrastructurally the coronet cells of Spar us saccus vasculosus resembled coronet cells described for other teleo sts, with an abundant smooth endoplasmic reticulum (SER) which was mor e highly organized in the coronets. IHC at EM level showed reaction ma inly with the membranes of the SER. These results suggest that S. aura ta saccus vasculosus may produce a PTHrP-like molecule similar to huma n PTHrP. (C) 1996 Academic Press, Inc.