IMAGE-ANALYSIS OF BROMODEOXYURIDINE (BRDU) STAINING FOR MEASUREMENT OF S-PHASE IN RAT AND MOUSE-LIVER

We developed a system for quantifying the numbers of bromodeoxyuridine (BrdU)-labeled hepatocyte nuclei in rat and mouse liver with an autom ated image analysis system. We began by developing a protocol for BrdU staining that would provide consistently intense staining to facilita te identification of both labeled and unlabeled nuclei by image analys is. Preliminary studies detected and characterized hepatocyte nuclei a nd differentiated them from non-hepatocyte nuclei using area and form factors. The parameters were selected to optimize discrimination betwe en the two populations, selecting 90% of hepatocyte and 5% non-hepatoc yte nuclei. Finally, we developed a program for automatic counting of BrdU-labeled hepatocyte and total hepatocyte nuclei. Results obtained from this method correlated well with data collected by a microscopist over a wide range of labeling indices. The automated system reduces i nterobserver variation and should minimize intraobserver error, as wel l as reducing the tedium of measuring labeling indices in the liver. M oreover, the techniques described should be applicable to other tissue s.