Stage-related variations in DNA fluorescence distribution during rat spermatogenic cycle measured by flow cytometry

Living segments of rat seminferous tubules representing the fourteen stages of the spermatogenic cycle have been isolated for DNA flow cytometry using the transillumination-assisted microdissection procedure. The resulting DNA profiles showed stage-related variations in the proportions of cells within the haploid (1C), diploid (2C) and tetraploid (4C) classes. Three distinct populations of haploid cells could be distinguished according to differences in fluorescence intensity of their nuclear DNA. The major haploid peak (1C) was found to reflect the steps 1-11 spermatids, the first hypofluorescent peak (fluorescence intensity from 0.45-0.75C) the steps 12-15 spermatids and the second hypofluorescent peak (fluorescence intensity of ca 0.25C) the maturing steps 16-19 spermatids. The changes in fluorescence intensity could thus be correlated with nuclear protein transitions that are known to occur during spermiogenesis in rats. The results indicated that tht processes responsible for the changes in nuclear fluorescence intensities are rapidly occurring, although not synchronously in all spermatids at the same developmental stages.