Vascularization of syngenic intracerebral RG2 and F98 rat transplantation tumors. A histochemical and morphometric study by use of ricinus communis agglutinin I.

The vascularization of intracerebral transplantation tumors of the two rat glioma clones RG2 and F98 was studied in various stages of progressive tumor growth by use of biotinylated Ricinus communis agglutinin I (B-RCA I) in avidin-biotin-peroxidase complex (ABC)-histochemistry. The tumors were induced by stereotactic implantation of 1000 glioma cells into the right caudate nucleus of 26 adult CDF-rats and examined after 10, 14, 18, and 21 days following controlled intracardial perfusion of the host animals. Our histochemical results on paraffin sections demonstrate that B-RCA I selectively stains vascular endothelial cells of arteries, veins, and capillaries not only in the normal rat brain but also in the transplantation tumors. Subsequently morphometric measurements of the B-RCA I-stained sections were performed to define the tumor vascularization in quantitative terms. There was an increase in the mean tumor vessel diameters during tumor growth in both transplantation tumor types leading to values about two times above those of the normal rat striatum. On the contrary, the mean vessel density and the mean vessel surface per tumor area were markedly reduced in the late stages of both tumor types when compared to the normal striatum. The RG2 and F98 transplantation tumors differed with regard to the intercapillary distance, which was two times higher in the F98 transplantation tumors than in the RG2 tumors on day 21. In conclusion, B-RCA I is a very sensitive histochemical marker for rat vascular endothelia on paraffin sections. Moreover, this method appears to provide the possibility for qualitative and quantitative study of the development of vasculature in intracerebral transplantation systems including tumors.