QUANTITATIVE COMPARISON BETWEEN THE GEL-FILM AND POLYVINYL-ALCOHOL METHODS FOR DEHYDROGENASE HISTOCHEMISTRY REVEALS DIFFERENT INTERCELLULARDISTRIBUTION PATTERNS OF GLUCOSE-6-PHOSPHATE AND LACTATE-DEHYDROGENASES IN MOUSE-LIVER

The precise histochemical localization and quantification of the activ ity of soluble dehydrogenases in unfixed cryostat sections requires th e use of tissue protectants. In this study, two protectants, polyvinyl alcohol (PVA) and agarose gel, were compared for assaying the activit y of lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G6PDH) in normal female mouse liver. Quantification of enzyme activi ty was determined cytophotometrically in periportal (PP), pericentral (PC) and midzonal (MZ) areas. No coloured reaction product was present in PVA media after the incubation period. In contrast, the agarose ge ls appeared to be highly coloured after incubation. As a consequence, sections incubated with gel media were less intensely stained than tho se incubated in PVA-containing media. The specific G6PDH reaction (tes t minus control) yielded approximately 75% less formazan in sections i ncubated by the agarose gel method than with the PVA method. Further, the amount of formazan deposits attributable to G6PDH activity was hig hest in the midzonal and pericentral zones of the liver lobule with PV A media, and Kupffer cells could be discriminated easily because of th eir high G6PDH activity. Significant zonal differences or Kupffer cell s could not be observed when agarose gel films were used for the detec tion of G6PDH activity. The LDH localization patterns appeared to be m ore uniform after incubation with both methods: no significant differe nces in specific test minus control reactions were seen between PP, PC and MZ. However, less formazan production (33%) was detected in secti ons incubated with agarose gels when compared with those incubated wit h PVA media. These results clearly show that the gel method is not sui table for the valid demonstration of activity of (partially) soluble e nzymes. Furthermore, our results confirm that a greater proportion of G6PDH than of LDH is present in a soluble form in liver cells.