Histochemical localization of carbonic anhydrase in the female genitalia of pigs during the oestrous cycle.

The ovaries and internal genital tracts of cycling gilts were studied for localization of carbonic anhydrase activity using a post-embedding cobalt precipitation technique. Carbonic anhydrase activity was present in selective capillary endothelia and epithelial cells of the genitalia. The ovarian parenchyma, irrespective of the stage of the oestrous cycle considered, was unstained. The secretory cells of the deep furrows in the uterotubal junction and those in the isthmic region of the oviduct of the oestrous female showed a clear membrane-bound localization. The surface epithelium in the tubal ampulla showed a conspicuous cytoplasmic carbonic anhydrase activity during oestrus and the early luteal phase. Neither the intensity nor the localization of the histo-enzymatic reaction in the females varied with their hormonal status (i.e. stage of the oestrous cycle). The localization of the enzyme in particular regions of the female pig genitalia that normally act as sperm reservoirs (uterotubal junction--tubal isthmus) or where fertilization--early embryo development occur (i.e. ampulla) might be related to the control of the acid-base status of luminal fluid.