RENAL-CELL TUMORS IN MICE - ELECTRON-MICROSCOPY VERSUS IMMUNOHISTOCHEMISTRY

15 renal cell tumours induced in CBA male mice by 1,2-dimethylhydrazin e were studied electronmicroscopically (EM). All these tumours earlier were investigated histochemically and immunohistochemically with the use of gammaglutamyltranspeptidase (GGT) as a marker of the proximal t ubules and antigen A(6) as a marker of distal tubules and/or collectin g ducts. One of the tumours was GGT-positive and antigen A(6)-negative and ultrastructurally well developed brush border was found. This cor relation between immunohistochemistry and EM data allowed to conclude that the site of origin of this tumour were the cells of the proximal tubules. All other tumours were GGT-negative and antigen A(6)-positive , i.e. the development of these tumours from the distal tubules (and n ot from the proximal tubules) could be suspected. However in 5 of thes e neoplasms reduced brush border was found. Microvilli were of a small er size than in normal proximal tubules and were frequently located no t on the apical cell surface but in the narrow spaces between two cell s. Invaginations and apical vesicles typical for the normal proximal t ubules were also found in some tumour cells. EM and immunohistochemica l data combined allow to suggest the origin of these tumours from the common precursor cell capable of differentiation, in the cource of tum our progression, into the cells with properties of proximal and/or dis tal tubules.