Induction and inhibition of testicular germ cell apoptosis by fluoroacetate in rats

Fluoroacetate (FA), an inhibitor of aconitase, is known to lower the intrac ellular level of adenosine triphosphate (ATP), which recently has been sugg ested to be a possible determinant of the form of cell death, apoptosis or necrosis. To investigate which form of germ cell death occurs in FR-induced testicular toxicity, adult Sprague Dawley rats were given a single oral do se of FA (0.5 or 1.0 mg/kg) and euthanized at 3, 6, 12, 24, 48, and 72 h th ereafter. Germ cell degeneration was histologically first found in early ro und spermatids at stage I and in spermatogonia at stages II-IV of seminifer ous tubules 6 and 12 h, respectively, after dosing. Degenerating spermatogo nia exhibited characteristic features of apoptosis as demonstrated by both electron microscopy and in situ terminal deoxynucleotidyl transferase-media ted dUTP nick end labeling (TUNEL), whereas spermatids did trot. At the 24 and 48 h time points, degenerating spermatids were continually present and subsequently formed multinucleated giant cells, while the number of degener ating spermatogonia and TUNEL-labeled spermatogonia was drastically and/or significantly decreased compared to those from the control group, indicatin g that spontaneous male germ cell apoptosis is inhibited. Coincident with t hese morphological changes, DNA laddering on gel electrophoresis was appare nt only 12 h after dosing. The results demonstrate that FA induces either a poptosis or necrosis of male germ cells in the early stage after dosing and subsequently inhibits spontaneous apoptosis.