Zinc in mammalian sperm: a review.

The relationship of zinc to morphologic, physiologic, and metabolic functions in the male reproductive system are summarized, and gaps in current understanding are pointed out. Semen and its constituents generally contain high zinc, although concentrations vary among animals and species; the relationships between zinc and fertility of semen is unclear. During zinc deficiency, retarded development of testicular growth involved marked atrophy of tubular epithelium and reduced deoxyribonucleic acid, ribonucleic acid, and protein, as well as reduced zinc contents of testis, epididymis, and dorsolateral prostate. Functions of zinc in hormone interrelationships are little understood, but zinc deficiency decreases output of pituitary gonadotrophins and androgen production, and zinc turnover involves testosterone as well as pituitary hormones. Metabolic regulation of sperm appears to be mediated through zinc as a regulator of enzyme activity in the semen. Within spermatozoa, zinc is closely associated with sulfhydryl groups and disulfide linkages and is concentrated in the tail. Control of motility of sperm by zinc apparently involves control of energy utilization through adenosine triphosphate systems involved in contraction and through regulation of phospholipid energy reserves. The many roles for zinc in the male reproductive system are extremely complex and scarcely understood. The importance of zinc contents of commonly utilized feedstuffs in relation to reproductive capabilities of the mammalian sperm remain unclear, although zinc deficiency in relation to male reproduction may be much more widespread than is recognized commonly.