Localization of carbonic anhydrase activity in the developing boar testis.

Embryonic and fetal pig gonads were obtained immediately after the sow's slaughter at 18, 21, 25, 28, 30, 36, 55, 63, 80 or 108 days of pregnancy. Semithin plastic sections were incubated for localization of carbonic anhydrase (CA) activity using a cobalt precipitation technique. In the embryonic gonad, CA activity was only present in the coelomic epithelium and in the endothelium of scattered blood capillaries. In the early testes (30-36 days) the CA activity was also localized in the cytoplasm of the sustentacular cells. Both spermatogonia and the developing interstitial cells were negative. At later stages, the testes presented a clear CA cytoplasmic activity in the Sertoli cells and a membrane-bound activity in the peritubular capillaries, resembling the enzymatic localization in the adult. The epithelium of the rete testis had a clear membrane-bound CA activity. CA histochemistry is useful as a marker for topographical studies of Sertoli cells during the prenatal development in the pig.