IMMUNOELECTRON MICROSCOPIC LOCALIZATION OF TESTICULAR AND SOMATIC CYTOCHROMES-C IN THE SEMINIFEROUS EPITHELIUM OF THE RAT

Somatic and testis-specific cytochromes c were localized ultrastructur ally in the seminiferous epithelium by immunocytochemistry using monos pecific antibodies. Cytochrome c(S) was lost from the mitochondria as spermatogenesis advanced, while there was a relative increase in cytoc hrome c(T) during the zygotene-to-pachytene transition; this was in ag reement with other studies that have suggested activation of the cytoc hrome c(T) gene during prophase of the first meiotic division. Cytochr ome c(T) was highly concentrated in mitochondria that were being degra ded within cytoplasmic lobes of spermatids and in residual bodies that were phagocytized by Sertoli cells. The two isoforms were found to co exist within the same mitochondrion during the transitional period fro m cytochrome c(S) to cytochrome c(T) predominance. In addition, both c ytochromes c were present in the chromatoid bodies of spermatocytes an d round spermatids; this suggests that the chromatoid body may be invo lved in the storage of these isozymes and possibly in their differenti al expression within germ cell mitochondria. Apocytochrome c was conce ntrated in mitochondria and chromatoid bodies of the germ cells and al so scattered in the cytoplasm. The presence of the holoprotein and apo protein immunoprobes within the chromatoid bodies of spermatocytes and spermatids was an interesting observation that raises questions regar ding the precise location of the synthesis of cytochromes c in spermat ogenic cells.