EFFECT OF AGE AND DIETARY RESTRICTION ON DAILY SPERM PRODUCTION AND NUMBER AND TRANSIT-TIME OF EPIDIDYMAL SPERMATOZOA IN THE MOUSE
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abstract
Dietary restriction extends the DNA repair capacity and life span of mice. Age-related changes in spermatogenesis and transit time of epididymal spermatozoa were evaluated to determine if dietary restriction altered the age-related changes in these traits as well. At weaning, mice were fed NIH-31 diet ad libitum or restricted to 60% of the ad libitum and sacrificed at 6, 12, 19, 22, or 26 months of age. The number of maturation phase spermatids or epididymal spermatozoa were counted by phase contrast cytometry of testicular or epididymal homogenates. Daily sperm production/testis (DSP/T) was determined by dividing the number of spermatids per testis by the 4.84 day life span of these spermatids. Daily sperm production per g parenchyma (DSP/G) was calculated by dividing DSP/T by the testicular parenchymal weight. Transit time of epididymal spermatozoa was calculated by dividing the number of epididymal spermatozoa by the DSP/T of the attached testis. Over both treatments, testicular and parenchymal weights were significantly decreased with age. While both DSP/G and DSP/T were similar (P>0.05) for 19, 22, and 26 months of age, they were lower (P<0.05) at 6 and 12 months of age, and there was a trend for them to be lower at 26 months of age. Age also reduced the number and the transit time of epididymal spermatozoa. DSP/G was not uniform in adult mice. Over all ages, dietary restriction had no significant effect on testicular weight or DSP/G, but it significantly reduced body and epididymal weight, number of epididymal spermatozoa, and epididymal spermatozoan transit time. Transit time of spermatozoa in the mouse epididymis was very long in younger adult mice, could vary widely, and was reduced by age and dietary restriction. Although not statistically significant, there was a trend for a delay in obtaining maximum DSP/T at 12 months and a delay in obtaining the age-related, reduced DSP/T at 26 months in the dietary restricted group compared to that seen in the ad libitum group. 1992 American Aging Association, Inc.
