AJP - Endocrinology and Metabolism, Vol 260, Issue 2 E286-E291, Copyright © 1991 by American Physiological Society
Characterization of vasoactive intestinal peptide receptors in rat seminal vesicle
L. G. Guijarro, M. S. Rodriguez-Pena and J. C. Prieto
Departamento de Bioquimica y Biologia Molecular, Universidad de Alcala, Alcala de Henares-Madrid, Spain.
Receptors for vasoactive intestinal peptide (VIP) in membranes from rat
seminal vesicle were examined using 125I-labeled VIP as ligand. The
receptor binding was rapid, reversible, saturable, specific, and dependent
on temperature and membrane concentration. At 15 degrees C, the
stoichiometric data suggested the presence of two classes of VIP receptors
with Kd values of 0.54 and 44.4 nM and binding capacities of 73 and 1,065
fmol VIP/mg membrane protein, respectively. The interaction showed a high
degree of specificity, as suggested by competition experiments with various
peptides structurally related to VIP as follows: helodermin was 10 times,
secretin 30 times, and rat growth hormone-releasing factor 300 times less
potent than VIP, whereas glucagon did not recognize VIP receptors in
concentrations of up to 10 microM. The binding of 125I-VIP to membranes was
sensitive to the presence of GTP in the incubation medium in a
dose-dependent manner. To characterize the molecular weight of these VIP
receptors, 125I-VIP was covalently bound to membranes from rat seminal
vesicle using dithiobis(succinimidyl propionate); sodium dodecyl
sulfate-polyacrylamide gel electrophoresis of the solubilized receptor
revealed the presence of a specific component with a molecular mass of
47,000 Da as estimated in denaturing conditions. These findings, together
with the known presence of VIP-containing nerves in the seminal vesicle,
suggest a direct physiological role for this peptide in this accessory
gland of the male genital tract.
