Effect of Antiandrogen on Calcitonin Gene-related Peptide Receptor of the Rat Gubernaculum

Cho, Su Youn; Shin, Myung Sik; Yoon, Moon Soo

Abstract

PURPOSE: We attempted to investigate whether calcitonin gene-related peptide binding to receptors in the gubernaculum is different between normal and flutamide-treated rats or pups and whether calcitonin gene-related peptide(CGRP) binding is androgen dependent.
MATERIALS AND METHODS
Timed pregnant Sprague Dawley rats were injected with flutamide or vehicle alone once daily on gestational days 15-19. Weight, anogenital distance and distance from testicle to symphisis pubis of pups of gestational day 20 and rats of neonatal day 1 and 7 were measured. Gubernacular sections from rats of neonatal day 7 were incubated with [125I]human CGRP with various concentrations of unlabeled hCGRP, and those from pups of gestational day 20 and rats of neonatal day 1 were incubated only with [125I]human CGRP. After exposure of gubernacular sections to imaging plate (BAS 2500), the images from the plate were quantified by computerized densitometry (TINA).
RESULTS
Weight and anogenital distance of flutamide-treated pups or neonatal rats were significantly smaller and shorter than those of normal pups or neonatal rats (P< 0.01). Though the distance from testicle to symphisis pubis was not significantly different between normal and flutamide-treated pups or neonatal 1 day rats, that of flutamide-treated neonatal 7 day rats was significantly longer than that of normal neonatal 7 day rats (P< 0.01). The total binding counts of [125I]human CGRP on gubernacular sections of normal pups, neonatal 1 day rats and neonatal 7 day rats were 56.3 +/- 24.74, 68.2 +/- 24.90, 78.4 +/- 17.25 (dpm/mg polymer), respectively, and those of flutamide- treated pups, neonatal 1 day rats and neonatal 7 day rats were 43.7 +/- 12.54, 35.1 +/- 8.25, 57.5 +/- 16.27, respectively. There were significant differences between normal and flutamide-treated neonatal 1 day and 7 day rats (P< 0.01). The binding in normal rats was consistently increased from gestational day 20 to neonatal day 7, and it showed weak correlation (r = 0.398, P< 0.05). The binding analysis showed that concentrations of CGRP receptors were 20.0+/- 4.78 amol/mg polymer, 13.3 +/- 3.87 amol/mg polymer for normal and flutamide treated neonatal 7 day rats, respectively, and there was significant difference between normal and flutamide-treated rats (P< 0.01). However there was no significant difference in the dissociation constant between 2 models. The images from the plate in flutamide-treated neonatal 7 day rats looked smaller than those in normal 7 day rats.
CONCLUSIONS
These results suggest that the inguinoscrotal descent of testicle occurs after the gubernacular eversion, CGRP binding in the gubernaculum is androgen dependent, and androgen may not influence CGRP release from genitofemoral nerve because of down regulation of CGRP receptor by antiandrogen. However, the role of CGRP in testicular descent is still obscure and the mechanism of down regulation of CGRP receptor by antiandrogen needs further investigation