EVIDENCE THAT GLUTATHIONE IS INVOLVED IN THERMOTOLERANCE OF PREIMPLANTATION MURINE EMBRYOS

Experiments were conducted to determine whether or not glutathione (GSH) is involved in thermotolerance responses of murine morulae. In the first experiment, morulae were exposed to either homeothermic temperature (37 degrees C), mild heat shock (40 degrees C for 1 h), severe heat shock (43 degrees C for 2 h), or a mild heat shock followed by severe heat shock (to induce thermotolerance). Exposure to mild heat shock did not affect viability and development, but severe heat shock reduced viability (i.e., live/dead staining) and the proportion of morulae that developed to blastocysts. This effect of 43 degrees C was reduced if embryos were first exposed to a mild heat shock of 40 degrees C. In the presence of DL-buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis, the ability of 40 degrees C to confer thermotolerance was reduced. BSO decreased embryonic GSH content but did not decrease overall protein synthesis. In another experiment, administration of S-adenosyl-L-methionine, an inducer of GSH synthesis, decreased the deleterious effects of heat shock of 43 degrees C for 2 h on viability and percentage of embryos that became blastocysts. Addition of 5 mu M GSH or GSH ester reduced the effect of 42 degrees C for 2 h on viability but not on continued development. The results suggest a role for GSH-dependent mechanisms in the processes by which murine embryos limit deleterious effects of heat shock.