Biomedical subjects
Publications and source records attributed to W W Wright.
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Aging of the mammalian testis is often accompanied by loss of germ cells and, as a result, decreased daily sperm production. It is currently unknown whether cell loss is the result of aging-related changes in germ cells or whether there are also aging-related changes in the Sertoli cells that normally support germ development and differentiation. To begin to compare the effects of age on germ cells and on Sertoli cells, we examined brown Norway rats of 6, 12, 18, 21, and 24 months of age for the frequency of seminiferous tubule regression and total testis contents of transcripts for three Sertoli cell products: SGP-2, transferrin, and cyclic protein-2 (CP-2)/cathepsin L. Histological analysis revealed no changes in the seminiferous epithelium from 6 to 12 months of age. However, from 12 to 24 months of age, the percentage of normal tubules gradually decreased from 95% to 15% of the total while the percentage of fully regressed tubules (containing no germ cells per tubule cross section) increased from 0% to 78%. In our analysis of specific Sertoli cell transcripts, we noted no change in total testis content of SGP-2 mRNA from 6 to 24 months. However, total testis content of transferrin mRNA was unchanged from 6 to 18 months, but increased by 24 months to 368% of the content of a 6-month-old testis. In contrast, total testis content of CP-2/cathepsin L mRNA was unchanged from 6 to 12 months, but decreased by 24 months to 58% of the content of a 6-month-old testis.(ABSTRACT TRUNCATED AT 250 WORDS)
In seeking an animal model of age-associated changes in the male reproductive tract, we examined the effects of age on the health and testicular steroidogenic activity of the Brown Norway rat, with comparisons made to the Sprague-Dawley rat. When perfused in vitro under conditions of maximally stimulating luteinizing hormone significant age-associated reductions were seen in testosterone production by testes of Sprague-Dawley rats of 21-24 months of age and by testes of Brown Norway rats of 18-30 months of age. Decreases in the capacity of the testes to produce testosterone were reflected in age-associated decreases in both serum testosterone and in testosterone concentration within the seminiferous tubule fluid. In contrast to the Sprague-Dawley rat, changes in steroidogenic activity in the Brown Norway rat were not accompanied by the occurrence of pituitary adenomas, obesity, or testicular tumors. This along with its longevity, make the Brown Norway strain a highly promising model for testicular aging.