Proto-oncogene products such as c-fos protein with a molecular weight
of 62 kDa have been identified in rat spermatocytes. In this study, ce
llular levels of c-fos proteins in spermatocytes, either with or witho
ut gossypol exposure, were quantitatively detected by Western immunobl
ot and a computer-controlled Spot-denso-program with an IS-1000 Digita
l Imaging System. Within 0.5-3.5 h (an average of 2 h) of the addition
of gossypol, levels of c-fos proteins fell dramatically. The reductio
n in c-fos proteins occurred G h before the apoptosis of spermatocytes
in the presence of gossypol. Four hours after exposure to gossypol, t
he c-fos protein content was overexpressed. The period of c-fos up-reg
ulation lasted for approximately 8 h. The increase in c-fos protein co
incided with a high rate of apoptotic cell death, Morphologic structur
e of the dying cell was revealed by electron microscopy. These results
suggest that spermatocyte apoptosis induced by gossypol correlates wi
th biphasic c-fos protein-mediated apoptosis. CONTRACEPTION 1998;57:28
1-286 (C) 1998 Elsevier Science Inc. All rights reserved.