The effects of centrifugation, various synthetic media and temperature on the motility and vitality of human spermatozoa.

The influence of various technical procedures and diluent media upon human spermatozoa has been tested in vitro. The percentage and velocity of motile spermatozoa were measured objectively using laser Doppler velocimetry. Vitality was determined by fluorescent staining. Centrifugation of semen (diluted 1 : 1 with Tyrode) at forces of 500, 800, 1 800 and 2 500 X g resulted in almost complete sedimentation of the spermatozoa. After resuspension in Tyrode's, spermatozoal motility was not changed significantly. The percentages of motile spermatozoa (measured at 37 degrees C) in Tyrode's and B2 medium remained the same as those in seminal plasma throughout an 8-hr period of incubation at 20 degrees C, while those in Locke's and phosphate-buffered saline (PBS) were significantly lower. The instantaneous modal velocities (Vc) of spermatozoa (also measured at 37 degrees C) in Locks's, Tyrode's and B2 were all significantly increased as compared to those observed in seminal plasma during incubation at 20 degrees C; spermatozoa in PBS showed a significantly reduced velocity compared to seminal plasma, but the difference was not significant. However, the rates of decline of the percentage of motile spermatozoa and of their velocities were indistinguishable in all four synthetic media and in the seminal plasma. No significant change in vitality was observed in any medium during the 8-hr incubation period at 20 degrees C. When spermatozoa were incubated at 37 degrees C, rapid declines in both percentage motile and in velocity were observed with incubation periods lasting more than 4-h. Subjecting the spermatozoa to a temperature of 4 degrees C for 1-h did not significantly change either of the motility parameters (measured at 37 degrees C), although prolonged exposure to 4 degrees C did greatly reduce their motility and velocity percentages. The decline in vitality was slow and uniform during incubation at either 4, 20 or 37 degrees C over periods of up to 10-hr, the best survival apparently being obtained at 20 degrees C and the worst at 4 degrees C, although there were no significant temperature differences at any time.