The current study was conducted on corpus luteum (CL) from healthy buffalo ovaries (n = 40) collected from local slaughterhouses. The CL was cleaned, observed grossly, and categorized into early luteal (stage I, 1 to 5 days), mid-luteal (stage II, 6 to 11 days), late luteal (stage III, 12 to 16 days), and regressing phase (stage IV, 17 to 20 days) based on their gross morphology, having ten ovaries in each group. The cryosections of CL obtained were incubated with substrates to study the

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... ution pattern of NADPH-diaphorase, NADH-diaphorase, and Non-specific esterase (NSE). The NADH-diaphorase activity was moderate within the developing luteal cells and weak in connective tissue in corpus haemorrhagicum, with strong to intense reaction in the luteal cells of mid-luteal phase CL and negligible activity in luteal cells of regressing phase. However, luteal cells of mid-luteal phase CL exhibited mixed activity for NADPH-d. In the corpus albicans phase, the NADPH-d activity was almost nil. NSE activity was moderate in the developing luteal cells in the corpus haemorrhagicum phase, strong in the luteal cells in mid-luteal phase, and moderate to weak activity for NSE within the cytoplasm of the regressing luteal cells. Therefore, it can be concluded that increased NADPH during the mid-luteal phase might be correlated to the increased secretory activity of cells as the enzyme is responsible for the conversion of cholesterol to progesterone and fatty acid synthesis. Histoenzymic localization of diaphorases and esterases in cyclic CL of buffalo, therefore, indicated their subsequent role in steroidogenesis.