Proliferative activity of human spermatogonia from fetal period to senility measured by cytophotometric DNA quantification.

The proliferative activity of human spermatogonia from the fetal period to senility was studied by means of cytophotometric quantification of the nuclear DNA content in histological sections. Proliferating spermatogonia that were replicating or had replicated their DNA (DNA content between 2.5c and 4.5c) were observed in all ages. The percentages of these spermatogonia were high (18.2%) in the second trimester of gestation, decreased in the third trimester (8.2%), maintained similar values in newborns (7.1%) and infants (9.5%), and increased markedly in 4- to 9-year-old children (22.5%). The latter percentage was maintained during puberty (20.1%), decreased significantly in adulthood (17.8%), and was higher in aging testes (25.2%). About 2% of spermatogonia with a DNA content higher than 4.5 c were observed from 4-15 years of age as well as in the testes of elderly men. Sertoli cells replicating their DNA were observed only in fetuses.