Zinc in the epididymal and vasal spermatozoa of rhesus monkey (Macaca mulatta)

Nuclear status of immature and mature stallion spermatozoa

'The highly packed chromatin of mature spermatozoa results from replacement of somatic-like histones by highly basic arginine- and cysteine-rich protamines during spermatogenesis, with additional conformational changes in chromatin structure during epididymal transit. The objective of the present study was to compare the nuclear characteristics of immature and mature epididymal stallion spermatozoa, using a variety of experimental approaches. Resistance to in vitro decondensation of chromatin, following exposure to SDS-DTT and alkaline thioglycolate, increased significantly in mature spermatozoa. Evaluation of the thiol-disulfide status (monobromobimane labeling) demonstrated that immature cells obtained from ductulli efferentes contained mostly thiol groups, whereas these groups were oxidized in mature cells collected from the cauda epididymidis. Based on atomic absorption spectrophotometry, maturation of stallion spermatozoa was accompanied by a 60% reduction in the Zn(2+) content of sperm cells, concomitant with increased concentrations of this ion in epididymal fluid. Furthermore, the degree of disulfide bonding was inversely correlated with susceptibility of chromatin to acid denaturation (SCSA). Collectively, these data were consistent with the hypothesis that maturation of stallion spermatozoa involves oxidation of sulphydryl groups to form intra- and intermolecular disulfide links between adjacent protamines, with loss of zinc as an integral feature. These changes endow mechanical and chemical resistance to the nucleus, ensuring efficient transmission of the paternal genome at fertilization.

The distribution of zinc in the subcellular fractions of the rhesus monkey testis

The zinc content in the testis of sexually immature, adult, and efferent duct-ligated adult rhesus monkeys was determined by atomic absorption spectrophotometry. Zinc content (μg/g wet wt) was found to be high in adult testis (165.9) when compared to immature (68.9) or efferent duct-ligated (104.2) animals. Analysis of subcellular fractions revealed that the concentration of zinc (expressed in relation to protein) was maximum in the microsomal fraction. The possible significance of this trace metal as a constituent of membrane proteins and enzymes, and as an activator of mitochondrial function in testis, is discussed.