Heat induced differential pattern of DNA fragmentation in male germ cells of rats.

Spermatogenesis being a highly dynamic processes is highly vulnerable to various stresses including heat stress. Though, the relationship between physiological temperature and male germ cells is certainly immense, the magnitude of spermatozoal damage after exposure to heat is evidently degree and dose dependent. Further, there are contradictory reports related to germ cells apoptosis in relation to temperatures. Thus, currently the dynamics of temperature and time dependence on germ cell apoptosis were studied by modulating the heat treatment strategies. It was observed that the rate of apoptosis increased initially then decreased with time. The DNA fragmentation in the 10,000×g supernatant of testis homogenate of rats that received heat treatment for 15-min, 30-min as well as 45-min treatment with 15-min intermittent period was found to be almost equal. In various heat treated animals, the apoptosis was found to be maximum after day-1 of treatments, which then followed a decreased pattern. These results indicate that there may be an initial induction of apoptosis in the germ cells, which later primed or programmed the other germ cells to activate protective mechanisms against heat induced DNA damage and thus protecting germ cell population to undergo apoptosis at later durations.

Conversion of apoptosis to necrosis and the corresponding alteration in the oxidative milieu of male germ cells of rat under acute heat stress: An experimental study.

BACKGROUND: Increased scrotal temperature can disrupt spermatogenesis leading to male infertility. Germ cells being heat sensitive maintain their genetic integrity via protective mechanism originated from the cell itself or by means of cell death. However, qualitative differentiation of how reactive oxygen species and antioxidant enzymes regulate signaling pathways of cellular damage including DNA fragmentation at varied temperatures remains unexplored. OBJECTIVE: The study was designed to evaluate the effects of heat mediated oxidative stress on male germ cells. Also, the time-dependent qualitative variation in the germ cell death was studied. MATERIALS AND METHODS: Thirty male Wistar rats were randomly segregated into five major groups (n=6/each) i.e., Control, 30, 45, 60, and 90-min counterparts according to heat treatment protocol. Quantitation of DNA and DNA ladder studies was performed along with various biochemical parameter like lipid peroxidation (LPO), glutathione, catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutatione reductase (GR), glutathione-s-transferase (GST). RESULTS: Animals receiving heat treatment for 30-min and 45-min revealed systematic and gradual response to heat stress; whereas, 60-min and 90-min treated animals showed a typical and abrupt change of the internal milieu of germ cells. Laddering and smearing effect of damaged DNA in 30 and 45 min and 60 and 90 min heat treated animals was seen respectively. CONCLUSION: As the duration of heat treatment increases, the rate of apoptosis reaches an optimum level, and a further increase in the duration of heat treatment converted the mode of cell death from apoptosis to necrosis, implicitly due to severe oxidative attack.