Properties of spermatozoa in relation to their elimination after vasectomy

Abstract

Sperm disposal and the formation of sperm granulomas are two related critical aspects of vasectomy which have been studied in man and several animal models. Since mammalian spermatozoa present a keratinoid quality, a comparison was made of the resistance of human and rat spermatozoa. When exposed to dithiothreitol and sodium dodecyl sulfate, human sperm decondense readily while rat sperm resist decondensation for long periods of time. A cooperative effect in the rate of decondensation was observed for human sperm but not for rat sperm. Oxidation of sulfhydryl groups renders human spermatozoa as resistant as rat spermatozoa, indicating that disulfide crosslinks are involved in this resistance. Human spermatozoa constitute a heterogeneous population with respect to sulfhydryl group content, suggesting variations in the state of maturation and/or elimination. The sulfhydryl group content of rat epididymal spermatozoa was similar from one cell to another, suggesting little sperm reabsorption in the epididymis. Human and rat spermatozoa differ in size, resistance to decondensing agents, cooperative effect during decondensation, and content and localization of sulfhydryl groups; these differences can explain why vasectomized rats invariably develop huge granulomas while this side effect is not severe in vasectomized men.

PIP: This study compares rat spermatozoa with human spermatozoa in respect to disulfide cross links; sulfhydryl group content; and resistance of the structures to chemical agents. The spermatozoa were decondensed, and whole sperm; sperm heads; and tails were counted in a Neubauer chamber and photographed under phase contrast microscopy. The spermatozoa were incubated; centrifuged; and resuspended in PBS for oxidation of sulfhydryl groups. For autoradiography, the spermatozoa were washed in PBS and exposed to a mixture of a maleimide compound and nonradioactive N-ethylmaleimide. Smears were prepared and the slides were developed with Kodak D19 developer. The autoradiograms were then analyzed for distribution and number of grains over the spermatozoa. Upon exposure to dithiothreitol and sodium dodecyl sulfate, human sperm decondensed readily while the rat sperm resisted decondensation for long periods of time. The human sperm exhibited a cooperative effect in the rate of decondensation but not the rat sperm. Oxidation of sulfhydryl groups rendered human sperm as resistant as rat spermatozoa, suggesting the involvement of the disulfide crosslinks in this resistance. Human spermatozoa are a heterogenous population with respect to sulfhydryl group content, indicating variations in the state of maturation and/or elimination. The differences between human and rat spermatozoa as to size; resistance to decondensing agents; cooperative effect during decondensation; and content and localization of sulfhydryl groups explain why vasectomized rats invariably develop huge granulomas while a small percentage of vasectomized men develop small granulomas.