Three consecutive-day injections with different doses (0.1, 0.25, 0.5, 1.0, 2.0 and 4.0 μg/g) of estradiol-17β (E2) produced statistically significant increases in the cytosolic NADP-linked malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in the ovary of the freshwater prawn (Macrobrachium rosenbergii) on the 4th day of treatment over the control values, depending upon the doses administered. Dose-dependent increases in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities were observed between 0.1–0.25, 0.25–0.5, and 0.5–1.0 μg/g doses. A similar magnitude of response was found at 1.0, 2.0 and 4.0 μg/g dose in both the cases of malate dehydrogenase and glucose-6-phosphate dehydrogenase activities. A lower dose of 0.5 μg/g was ineffective in eliciting any response to either enzyme. Ergosterol (2.0 μg/g) did not evoke any change in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in comparison to the control values.