Abstract
Abstract
Phenotypically distinct but genetically identical obese mottled yellow A vy /a and lean pseudoagouti A vy /a sibling mice and their congeneic black a/a littermates provide an experimental system for distinguishing phenotypic effects from genotypic effects in the expression of the genotype at the organismic level. Hepatic glutathione S-transferase activity in obese yellow A vy /a (YS × VY) F-1 hybrid female mice was only about 66% of that found in their lean black a/a sisters. This decreased enzyme activity was not a direct effect of the A vy /a genotype but was associated with the obesity of the yellow mice since the enzyme activity in lean pseudoagouti A vy /a female siblings was similar to that found in the black a/a mice. Long-term feeding of 160 ppm lindane in the diet decreased the enzyme activity in all phenotypes but did not eliminate the difference between the obese yellow and lean pseudoagouti and black mice. Interpretation of the available data suggests that no direct relationship exists between the level of hepatic glutathione S-transferase activity and the enhancement of tumor formation in yellow A vy /a mice. Several inbred mouse strains and F-1 hybrids were also screened for this enzyme activity. No strain differences were found but sex differences within different inbred strains were not uniform. In the AE and YS strains and their F-1 hybrid enzyme activity was higher in females than in males. In contrast, BALB/c and VY strain males had higher enzyme activity than the corresponding females.
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