LEYDIG-CELL APOPTOSIS IN THE RAT TESTES AFTER ADMINISTRATION OF THE CYTOTOXIN ETHANE DIMETHANESULFONATE - ROLE OF THE BCL-2 FAMILY MEMBERS

Ethane dimethanesulphonate (EDS) is cytotoxic to Leydig cells in the a dult rat. To investigate the role and regulation of apoptosis in the L eydig cell, EDS (100 mg/kg i.p.) was administered to adult male rats a nd the testes examined 6, 12, 18, 24, 18 and 72 h later. Numbers of Le ydig cells, identified by 3 beta-hydroxysteroid dehydrogenase immunohi stochemistry started to fall by 12 h after EDS injection and were almo st undetectable by 72 h. Apoptotic cells in the insterstitium, visuali sed by in situ end labelling of DNA, increased in number to reach a ma ximum 24 h after injection of EDS, and were undetectable by 72 h. In m any tissues the apoptosis-related gene products act in cohort: Bcl-2 a nd Bcl-xl promoting survival of a cell, whilst Bar promotes cell death often positively regulated by the tumour-suppressor gene p53. Western blot analysis showed that: (1) Bcl-2 and p53 were absent from interst itial Leydig cells but were expressed in the seminiferous tubules. (2) Bar protein although expressed in the interstitium was not present in the Leydig cells. (3) Bcl-xl in Leydig cells was transiently increase d after EDS. In conclusion, EDS kills Leydig cells by apoptosis; howev er the control of Leydig cell death does not involve p53 or the Bcl-2 family members but may require other gene products yet to be identifie d.