NADP-dependent dehydrogenases in rat liver parenchyma. II. Comparison of qualitative and quantitative G6PDH...

Qualitative histochemical G6PDH distribution patterns obtained in the liver acinus of adult male and female rats with an improved method (Rieder et al., 1978) served as a basis for the isolation by microdissection of tissue samples of defined zonal affiliation. G6PDH activity was assayed quantitatively in tissue samples of zones 1 and 3 by a microfluorometric method, using the oil well technique and enzymatic cycling (Burch et al., 1963; Lowry and Passonneau, 1972). With the use of a correlation system further evidence could be presented for the validity of the recently described qualitative distribution patterns. From a total of 50 analyzed tissue samples the following G6PDH activities were calculated: 4.25 +/- 1.56 U/g dry weight in zone 1 and 2.08 +/- 0.46 U/g dry weight in zone 3 of male and 7.21 +/- 1.03 U/g dry weight in zone 1 and 11.10 +/- 2.56 U/g dry weight in zone 3 of female rats. These data were corrected for interference from the G6PDH activity of the Kupffer cells within zone 1 samples (approximately 80 U/g dry weight), so that the actual relative values for the parenchymal activity could be estimated for the first time: 2 U/g dry weight in zones 1 and 3 of male animals, 5 U/g dry weight in zone 1 and 11 U/g dry weight in zone 3 of female animals. In female livers G6PDH activity in zone 1 is therefore 2.5 times higher, and in zone 3 5 times higher than in the male. These zonal as well as sex-differences are clearly indicative of a heterogeneous functional organization of the liver acinus in terms of capacity for NADPH production, mainly in connection with reductive reactions in fatty acid synthesis.