The role of mRNA levels and cellular localization in controlling sn-glycerol-3-phosphate dehydrogenase expression in tissues of the mouse.

sn-Glycerol-3-phosphate dehydrogenase (glycerol-P dehydrogenase, EC 1.1.1.8) activity levels in seven tissues of adult mice vary approximately 100-fold from a low of 0.1 unit/mg of protein in the cerebral cortex to a high of 8 units/mg of protein in the brown fat of cold-adapted mice; the brown fat accounts for approximately 1% of the total tissue protein. This high degree of variation in the quantitative expression of an enzyme in different tissues has provided us with a system for analyzing the mechanism by which tissue specific variation for a given gene product is controlled. To this end we have measured the amount of immunoreactive enzyme and the level of translatable glycerol-P dehydrogenase mRNA and have localized the glycerol-P dehydrogenase-positive cells by immunocytochemistry. We have found that the amount of enzyme protein in a tissue is strongly correlated with the level of its translatable mRNA (correlation coefficient = 0.996) and that in several cases the differences among tissues can be explained by differences in the numbers of glycerol-P dehydrogenase-positive cells.