THE CORRELATES AND ALLEGED BIOCHEMICAL BACKGROUND OF THE RESAZURIN REDUCTION TEST IN SEMEN

Reduction of the blue dye resazurin to pink resorufin is used to estim ate the concentration of metabolically active spermatozoa in semen sam ples. In order to quantify the reduction of resazurin, a spectrophotom etric method was developed measuring the change from blue to pink; in the butanol extracted colour. The biochemical mechanisms involved in t he reduction oi resazurin by motile spermatozoa and seminal plasma. we re investigated. Addition of NADH + H+ to sperm suspension or seminal plasma increased the reduction of resazurin. The reduction reaction wa s inhibited by high concentrations of dicoumarol, a specific inhibitor of the diaphorase enzyme, in a dose-dependent manner. It is suggested that the sperm diaphorase enzyme transfers electrons from NADH + H+ t o resazurin, reducing it to resorufin. The degree of resazurin reducti on mas strongly correlated with the concentration of motile spermatozo a recovered from the 90% Percoll fraction (r = 0.98, p < 0.001). A pos itive correlation was also found between the reducing capacity of semi nal plasma (n = 62) on the one hand, and sperm concentration (r = 0.72 , p < 0.0001), progressive motility (r = 0.45, p < 0.01), normal morph ology (r = 0.50, p < 0.01), and gamma-glutamyltransferase (r = 0.36, p < 0.05) on the other hand. These findings, together with our previous observations that the reduction reaction is inhibited by reactive oxy gen species and polymorphonuclear white. blood cells, increase our und erstanding of the biochemical basis oi the resazurin test and may prov ide better insight into the interpretation of this test.