Detection of different cellular sides in rat liver and kidney by two monoclonal antibodies raised against the nucleotide-sugar hydrolyzing enzymes phosphodiesterase I and CMP-sialic acid hydrolase.

Six different monoclonal antibodies were generated after immunization of mice with a partially purified enzyme preparation of rat liver, containing nucleotide-sugar hydrolase (NSH) I and II. These enzymes are also known under the names phosphodiesterase I and CMP-sialic acid hydrolase respectively [11]. In the enzyme-immunoassay the antibodies directed against NSH I displayed some cross-reactivity with the enzyme preparation of NSH II, and to a much lower extent the reverse was also true. Two antibodies, C and D highly reactive with NSH II and NSH I respectively, were used for immunocytochemical studies on sections of various rat tissues, which were known to contain high activities of both enzymes. Both antibodies were shown to be highly specific domain markers for different sides of the various cells. Antibody C was bound exclusively to the sinusoidal side of liver hepatocytes and to the basal side of cells from kidney tubule and epididymis. For antibody D the binding pattern was completely different, showing exclusive binding to the canalicular side of the hepatocytes and to the brush border membranes of kidney tubule cells, whereas in epididymis only binding to connective tissues was observed. Our studies clearly demonstrate, at least for liver and kidney, that NSH I and II are located at different cellular sides and that the monoclonal antibodies C and D can be used as domain markers for basal and apical sides of these cells respectively.