Localization of a protein inhibitor of carbonic anhydrase in pig tissues

ABSTRACT The protein inhibitor of carbonic anhydrase (CA), pICA, was localized in pig tissues by an immunohistochemical technique, using rabbit antipICA IgG. Staining for pICA was found in liver sinusoids and kidney glomeruli, where phagocytic cells are located, i.e. Kupffer and mesangial cells, respectively. pICA was not found inside parenchymal cells, or in tissues from striated muscle, heart, eye or lung. It is concluded that the function of pICA is perhaps to bind the carbonic anhydrase isozymes CA I, II, and III, released from erythrocytes into the blood circulation by intravascular haemolysis. The complex of CA‐pICA in plasma may then be transported to the reticuloendothelial system, for degradation and reclamation of CA‐bound zinc. This would be similar to the fate of the haemoglobin–haptoglobin complex for the recycling of iron.