A fluorescent analogue of hydrin 1: a new probe for vasotocin receptors.
Hydrin 1 is the biosynthetic precursor of vasotocin in Xenopus laevis. We have synthesized deamino and fluorescein analogues of hydrin 1 and characterized their physiological action in the urinary bladder of the toad, Bufo marinus. 1-Deamino-hydrin 1 (d-hydrin) was more potent than vasotocin in stimulating osmotic water flow across intact bladders and more potent than vasotocin in displacing tritium-labeled vasopressin [( 3H]AVP) from cell membranes. 1-Deamino-[11-lysine (fluorescein)]-hydrin 1 (flu-hydrin) was found to be the most potent fluorescent vasotocin receptor probe synthesized to date. Flu-hydrin increased osmotic water flow across bladders with a half-maximal effective dose (ED50) value of 6 x 10(-10) M and displaced [3H]AVP from membranes with a half-maximal concentration (IC50) value of 3 x 10(-9) M. The hydrosmotic response to flu-hydrin was blocked by 1-deamino-[4-lysine (p-azido-benzoyl)]arginine vasotocin [d4Lys(N3)-AVT]. Epifluorescence light microscopic studies showed vesicular uptake of flu-hydrin at the basolateral membrane of toad bladder epithelial cells, and this uptake was blocked by d4Lys(N3)AVT. This study shows that d-hydrin can serve as a foundation molecule to which reporter groups, such as fluorescent residues, can be attached with better preservation of hydrosmotic activity than is possible with similar modifications of vasotocin.
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Department of Physiology and Biophysics, Mount Sinai Medical Schools, City University of New York, New York 10029.
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D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D002024:Bufo marinus; D005260:Female; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D010539:Permeability; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000378:metabolism*; D017483:Receptors, Vasopressin; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*; D014668:Vasotocin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D014982:Xenopus laevis
D005456:Fluorescent Dyes; D011945:Receptors, Angiotensin; D017483:Receptors, Vasopressin; C034862:vasotocin receptor; C060257:hydrin 1; D014668:Vasotocin