AJP - Endocrinology and Metabolism, Vol 259, Issue 4 E524-E528, Copyright © 1990 by American Physiological Society
A fluorescent analogue of hydrin 1: a new probe for vasotocin receptors
P. Eggena, C. L. Ma, M. Q. Lu and A. Buku
Department of Physiology and Biophysics, Mount Sinai Medical Schools, City University of New York, New York 10029.
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.
