LOCALIZATION OF CARBONIC-ANHYDRASE IN THE SPERM STORING REGIONS OF THE DOMESTIC HEN OVIDUCT

In the female bird sperm is stored in a quiescent mode, but full motil ity is needed for successful fertilisation. Regulation of sperm motili ty is thus of vital interest and the pH is a factor of importance. For this reason the localisation of carbonic anhydrase in the vagina, ute rovaginal junction and infundibulum was studied with a histochemical m ethod. Carbonic anhydrase catalyses the reaction CO2+H2O<->H++HCO3- an d is known to take significant part in acid-base regulation in the bod y. The enzyme was found in all regions with the highest activity, both cytoplasmic and membrane-bound, in the non-ciliated cells of the uter ovaginal surface epithelium. Intense membrane-bound activity was also found in both the infundibular grooves and glands with slightly less i n the sperm storage tubules and vaginal epithelium. Occasionally cytop lasmic and nuclear staining was seen. Changes in pH affect sperm motil ity and our results provide the first evidence for cellular mechanisms that makes rapid changes of the pH possible in these regions. Judging from the distribution of carbonic anhydrase we suggest two possible f unctions: (1) increasing pH and/or adding bicarbonate ions to stimulat e sperm motility needed for the transfer to the storage sites and at f ertilisation, and (2) a lowering of the pH in the sperm storage sites to keep the sperm quiescent during storage.