# Use of \alpha - and \delta -subunit specific antibodies in studying interaction of hCG with Leydig cell receptors

Dighe, RR and Moudgal, NR (1983) Use of \alpha - and \delta -subunit specific antibodies in studying interaction of hCG with Leydig cell receptors. In: Archives of Biochemistry and Biophysics, 225 (2). pp. 490-499.

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## Abstract

Antisera (a/s) raised to individual \alpha - and \delta -subunits of human chorionic gonadotropin (hCG) [9002-61-3] were characterized for specificity and used to study the disposition of the 2 subunits when intact hCG is complexed with LH [9002-67-9] receptor of the Leydig cells. The ability of the preformed hormone-antibody (H-Ab) complex to bind to receptor and stimulate a response; the ability of the a/s to dissoc. hCG from its complex with the receptor and thereby terminate response; and the ability of the premixed antibody and receptor to compete for binding of labeled hCG were examd. Although the subunit specific a/s were equipotent in binding hCG, their behavior once the receptor prepn. of Leydig cell is introduced into the system was drastically different. The \delta -subunit antibody relative to the \alpha -subunit antibody was poorly effective in preventing hCG from either binding to the receptor or inhibiting the continuation of response. Apparently, hCG upon interaction with the receptor loses the determinants specific to the \delta -region more rapidly than those specific to the \alpha -region suggesting that the initial interaction of hCG with the receptor occurs through sites in the \delta -subunit. Although the \alpha -subunit portion of the hCG mol. is available for binding to the antibody for a relatively longer time, the biol. response of the cell seems very sensitive to such binding with the antibody as it invariably results in loss of response. In the Leydig cell system, the ability of the a/s to bind hCG that is already complexed to the receptor appears dependent upon the time of addn. of the antibody to the incubation medium. The antisera were totally ineffective in inhibiting steroidogenic response to hCG if added 60 min after addn. of hCG. The hormone-receptor complex once formed, perhaps continues to change its orientation with the result that with time relatively less and less of antigenic determinants become available for antibody binding

Item Type: Journal Article Copyright belongs to Elsevier Science Division of Biological Sciences > Biochemistry 28 Mar 2008 19 Sep 2010 04:43 http://eprints.iisc.ernet.in/id/eprint/13523