Histoenzymology of the lung. Some enzymic activities of capillary endothelia of the rabbit alveolar walls.

Mg-dependent ATP-ase, alkaline phosphatase and carbonic anhydrase activities were tested at the level of capillary endothelia of alveolar walls in normal rabbits. A constant and relatively intense activity within these endothelia appeared to be that of the Mg-dependent ATP-ase. The carbonic anhydrase activity marked some endothelia, and the alkaline phosphatase was unequally demonstrable at this level. These different histoenzymic aspects might reflect the unequal activity during time and space of these enzymes at the level of capillary endothelia of alveolar walls.