Glutathione peroxidase in bovine semen

The roles ofselenium (Se) and glutathione peroxidase in reproductive function are poorly understood, but it is possible that they may be important for normal reproduction in the male. In rats fed a Se-deficient diet, the testes accumulated and retained more 75Se than did other tissues 1 week after injection (Brown & Burk, 1972; Burk, Brown, Seely & Scaief, 1972). Autoradiographic studies(Brown & Burk, 1972) of spermatozoa recovered from rat epididymides have shown that 75Se is associated with the midpiece of the spermatozoon. Gould (1970) has suggested that 75Se is probably incorporated into late spermatocytes or early spermatids in the rat. Rotruck et al. (1973) demon-strated that Se is a component of glutathione peroxidase, an enzyme which has been reported to exist in dog, goat, ram and human semen (Li, 1975). The objectives of the present study were to determine whether glutathione peroxidase is present in ejaculated bovine semen and the relationship of the enzyme levels to sperm concentration and ejaculate volume. The first 2 successive ejaculates from each of 10 mature dairy bulls were collected by means of an artificial vagina. Immediately after collection and determination of ejaculate volume, sperm con¬ centration and percentage of motile spermatozoa, 0-4 ml whole semen was packaged in 1-ml glass ampoules and frozen in N2 vapour until assayed for glutathione peroxidase. The percentage ofmotile spermatozoa ranged from 40 to 70 % with a mean motility for all ejaculates of 63 %. At the time o