CHANGES IN ATP LEVEL AND IRON-INDUCED ULTRA-WEAK PHOTON-EMISSION IN BULL SPERMATOZOA, CAUSED BY MEMBRANE PEROXIDATION DURING THERMAL-STRESS

ATP level, cell motility and viability, oxygen uptake, pyruvate kinase activity, and ultra-weak photon emission (UPE) induced by red-ox Fe2-ascorbate cycling system were studied in fresh, in previously equilib rated in a glycerol diluent, and in cryopreserved bull spermatozoa, ex posed to thermal stress by incubation of the cells at 44 degrees C. A sharp drop in motility and viability of fresh spermatozoa and even mor e so, of equilibrated and cryopreserved cells was accompanied by accum ulation of ATP. When cell movement was totally inhibited, ATP utilizat ion was decreased, while chemical energy continued to be produced by c ell pyruvate kinase, one of the key glycolytic enzymes, which in sperm atozoa is very active (6500 IU/g protein) and insensitive to feed-back inhibition by excess of ATP and L-cysteine. Accumulation of ATP durin g incubation at 44 degrees C in 0.9% NaCl was accompanied by a rapid d ecrease in oxygen consumption by fresh spermatozoa and an increase in Fe2+-ascorbate induced UPE, followed by a sharp decrease in ATP level observed at the end of induced UPE measurement. The increase in photon emission due to lipid peroxidation was highly correlated with the inc rease in cell ATP level caused by thermal stress.