Ribosomal RNA synthesis in spermatogonia and sertoli cells of the mouse testis

Abstract

With the aim of characterizing the biochemical and functional activity of the various types of testicular cells in the mouse, an attempt of partial separation of these different cell classes was done using ionizing radiation which at low doses and at short intervals after irradiation destroys selectively the spermatogonia without affecting the other germ cells and the Sertoli cells. Swiss male albino mice were irradiated with 300 rads of X-rays and were 40 h later injected intraperitoneally with 32P-ortophosphate. As previously demonstrated by others histological tests showed that at this interval after irradiation almost no spermatogonia are present, whereas the spermatocytes and the Sertoli cells appear normal in number and morphology. At fixed intervals after labelling, the ribosomal RNA was extracted and analyzed by sucrose gradient sedimentation. Preliminary experiments have ruled out radiation effects on the rate of incorporation or of breakdown of the radioactive RNA within this dose range. The results have demonstrated that ribosomal RNA is actively synthesized both in the control and irradiated seminiferous tubules. Since previous autoradiographic experiments have demonstrated that spermatocytes do not synthesize ribosomal RNA precursors and since middle and late spermatids are inactive in RNA synthesis, the quantitative comparison between the radioactivity incorporated into 18S and 28S ribosomal RNA in the control and that incorporated in the irradiated testes indicates the relative participation of spermatogonia and Sertoli cells in the synthesis of ribosomal RNA. These experiments represent a preliminary approach for the biochemical characterization of the various stages of spermatogenesis.