title: Tyrosine phosphorylation is a novel pathway for regulation of chloride secretion in shark rectal gland.
abstract: We used the specific tyrosine kinase inhibitor genistein to define the involvement of tyrosine phosphorylation in the regulation of chloride transport in the rectal gland of the dogfish shark, a model for chloride secretion via a cystic fibrosis transmembrane conductance regulator (CFTR)-like channel. In the perfused gland, genistein (100 microM) promptly increased chloride secretion from basal values of 159 +/- 36 to 966 +/- 49 mueq.h-1.g-1 (P < 0.0001). Bumentanide fully reversed genistein-induced secretion. In primary culture monolayers of rectal gland tubular cells, genistein, but not the inactive 7-glucoside form, genistin, increased short-circuit current in a dose-dependent manner, from basal values of 2.7 +/- 4.3 to 104 +/- 10 microA/cm2 (P < 0.0001). Apically applied genistein induced significantly greater chloride secretion than basolateral addition. Genistein did not increase the adenosine 3',5'-cyclic monophosphate (cAMP) content of either perfused glands or cultured monolayers. Using an anti-phosphotyrosine antibody, we observed phosphorylation of multiple proteins. Four peptides, with molecular masses of 250, 210, 55, and 53 kDa, responded to genistein treatment with a decrease in tyrosine phosphorylation. These data demonstrate the following: 1) genistein induces bumetanide-sensitive chloride secretion in both perfused rectal glands and cultured tubular cells; 2) these effects are not accompanied by an elevation of tissue cAMP, indicating that genistein-induced secretion is not mediated by the cAMP-protein kinase A pathway; and 3) genistein-sensitive peptides are present in the rectal gland cell and are candidates for involvement in the regulation of chloride secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D008297:Male; D010455:Peptides / Q000378:metabolism; D010477:Perfusion; D010766:Phosphorylation / Q000187:drug effects; D012491:Salt Gland / Q000378:metabolism*; D012754:Sharks / Q000378:metabolism*; D014443:Tyrosine / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002712:Chlorides; D007529:Isoflavones; D010455:Peptides; D014443:Tyrosine; D019833:Genistein; D000242:Cyclic AMP