Nitric oxide: [alpha] modulator for the epidermal growth factor receptor expression in developing ovarian granulosa cells. Hattori, Masa-Aki, Kenji Sakamoto, Noboru Fujihara, and Itaru Kojima. Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371, Tsumura Research Institute for Pharmacology, 3586 Yoshiwara, Amicho. Inashiki-gun, Ibaragi 300-11, Laboratory of Animal Reproduction, Department of Animal Science, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812, Japan
APStracts 2:0368C, 1995.
The present study was designed to assess the involvement of nitric oxide (NO) in the regulation of EGF receptor during development of rat granulosa cells, which were prepared by puncturing ovaries of diethylstilbestrol-treated rats. The immature cells were cultured for 48 h with follicle-stimulating hormone (FSH) to be transformed into mature cells. A marked accumulation of cGMP was observed during development. The accumulation of cGMP, but not of cAMP, was suppressed by specific inhibitors of NO synthase, L-NG-monomethyl-L -arginine (L-NMMA) and L-NG-nitro-L-arginine (L-NNA), and [alpha] selective inhibitor of the inducible NO synthase, aminoguanidine. The L-NMMA-induced suppression was partially reversed by addition of L -arginine to cultures but not D-arginine, indicating that NO formation is inhibited by competing with analogs of L-arginine for NO synthase. Treatment with carboxyl-PTIO, an antagonist of NO, caused suppression in the increase of EGF binding sites, whereas exposure of the cells to sodium nitroprusside (SNP), an NO donor, caused elevation in EGF binding sites, with increasing extra- and intra-cellular cGMP levels. Analysis of the EGF receptor by affinity-labeling with 125I-EGF revealed that the intensity of the cross-linked receptor molecule with a molecular mass of 180 kDa was increased by exposure to SNP. The facilitatory effect of SNP on the EGF receptor was observed when cAMP-dependent pathway was fully activated by FSH. However, the NO effect may be mediated by a cGMP-independent pathway, as 8-bromo-cGMP did not mimic the action of SNP. These results indicate that the L -arginine-NO system may contribute to the regulation of EGF receptor expression in developing granulosa cells stimulated by FSH. 

Received 13 July 1995; accepted in final form 18 September 1995.
APS Manuscript Number C424-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95