In rat liver, the total amount of NAD and NADH is approximately 1 μmole per gram of wet weight, about 10 times the concentration of NADP and NADPH in the same cells. The actual concentration of NAD in cell cytosol is harder to measure, with recent estimates in animal cells ranging around 0.3 mM, and approximately 1.0 to 2.0 mM in yeast.</ref> However, more than 80% of NADH fluorescence in mitochondria is from bound form, so the concentration in solution is much lower.