Background Parenchyma Research Articles

Effect of modifying agents on the phenotypic expression of cytochrome P-450, glutathione S-transferase molecular forms, microsomal epoxide hydrolase, glucose-6-phosphate dehydrogenase and γ-glutamyltranspeptidase in rat liver preneoplastic lesions

The expression of A and P forms of glutathione S-transferase (GST-A and P), two cytochrome P-450 isoenzymes (P-450 PB3a and P-450 MC2), microsomal epoxide hydrolase (mEHb), glucose-6-phosphate dehydrogenase (G6PD) and gamma-glutamyltranspeptidase (gamma-GT) was compared in preneoplastic liver lesions and background parenchyma of F344 rats post-treated with butylated hydroxyanisole (BHA), ethoxyquin (EQ) or acetaminophen (AAP). These latter three compounds have been shown to inhibit hepatocarcinogenesis after initial treatment with N-ethyl-N-hydroxyethylnitrosamine (EHEN) and a significant decrease in the number of enzyme-altered foci and nodules positive for GST-P, GST-A, G6PD and gamma-GT and negative for P-450 PB3a, P-450 MC2 was associated with their administration. Whereas in the foci case the decrease was most prominent for non-discrete (heterogeneous) type lesions, the results of quantitation of nodules revealed a most significant alteration in the discrete homogeneously staining population. This indicates that BHA, EQ and AAP have the potential to inhibit the growth of the phenotypically stable lesions thought most likely to be the immediate precursors of hepatocellular carcinomas. The two anti-oxidants were associated with periportal increase of all enzymes investigated, whereas AAP induced GST species and mEHb in the perivenular zone. Irrespective of slightly elevated enzyme levels in surrounding parenchyma, mEHb antibody binding levels within lesions showed a reciprocal shift from positive to negative in rats treated with BHA, EQ and AAP.

A methodological approach to rapid and sensitive monoamine histofluorescence using a modified glyoxylic acid technique: the SPG method.

A modified approach of the glyoxylic acid (GA) condensation reaction for the visualization of biogenic amines in tissue is described. Cryostat sections are used from brain or extracerebral tissue in dog, monkey, rat and mouse and exposed for 3 s to a room temperature solution containing sucrose-potassium phosphate-glyoxylic acid (SPG). The tissues are air dried and heated in an oven for 5 min. The complete precessing time from fresh tissue to microscopic examineation takes 18 min. Morphologically sharp and brightly fluorescent monoamine-containing neurons, pre- and terminal axons are seen against a dark parenchymal background without drug pre-treatment. The SPG method retains the high specific sensitivity for monoamines previously described in the original technique but is, in addition, more rapid and simple and is easily accissible as a research tool to investigators inexperienced in histofluoresecence techniques.