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The Nature of a Yeast-Stimulating Agent in Mammalian Spermatozoa¹

University of Wisconsin^,3

Abstract

A search for the cause of differences in the metabolic characteristics between bovine spermatozoa obtained from ejaculated semen and those collected from excised epididymides has led to the finding that extracts of semen stimulate respiration and glycolysis of epididymal spermatozoa and fermentation of yeast.

A method has been described for the biological assay of the yeast-stimulating substance.

The yeast-stimulating substance can be obtained from semen of the bull, ram, boar, rabbit, and man. It can also be obtained from testis tissue but not, by the same procedures, from a variety of other tissues.

On the basis of yeast assay the regulator seems to occur in a bound inactive form in epididymal or freshly ejaculated spermatozoa from which, under the influence of seminal fluid, it is progressively liberated into the medium, presumably in a combination still inactive for yeast cells. The yeast-active component can be liberated by mild alkaline hydrolysis of spermatozoa or whole semen.

A method has been described for preparing partially purified concentrates of regulator from semen suitable for studying its biochemical significance. The yeast-active principle has been isolated in crystalline form from hog testis extract and identified as elemental sulfur.

¹ Published with the approval of the Director of the Wisconsin Agricultural Experiment Station. Supported in part by grants from the Rockefeller Foundation, the Badger Breeders Cooperative and the Brittingham Trust Fund. This is paper No. 1 in a series entitled: Regulation of Metabolism in Mammalian Spermatozoa.

² We are indebted to the Department of Dairy Husbandry, University of Wisconsin, the Badger Breeders Cooperative and the Wisconsin Scientific Breeding Institute for generous supplies of bull semen. Prof. L. E. Casida kindly provided the boar, ram and rabbit semen from his experimental animals.

^3s Department of Biochemistry.