Effect of ejaculation frequency on the water volume of rabbit spermatozoa as determined by electron spin resonance spectroscopy.

Abstract

An electron spin resonance (ESR) technique using 2 lI-Tempone to measure the water-accessible volume of rabbit spermatozia was evaluated. We determined that the ESR signal from 2 H-Tempone in buffer decayed after being combined with spermatozoa and that the rate of decay was variable among sperm samples. To reduce variation in sperm voiume determinations, a method was developed that accounts for the decay during the period of observation. ESR of 2 FI-Tempone also was used to measure the water-accessible volume of sperm from rabbits ejaculated once daily for 4 days following a 1-2-week sexual rest. Under this regimen, the average water volume determined by ESR declined from 15 �.zm’ on the first day of ejaculation to 6.3 kim’ on the fourth successive day of ejaculation. However, no corresponding decrease was observed in dimensions of sperm in photomicrographs. We concluded that the nature of the interaction of sperm and 2 H-Tempone was affected by the ejaculation frequency of the animal providing the sample, resulting in a decreased ESR signal but not a real decrease in sperm volume. Although the biological significance of these observations is not yet understood, we suggest that the ejaculation regimen of an animal should be considered when determining sperm water volume using ESR.