Cytochemical localization of nicotinamide adenine dinucleotide phosphatase (NADPase) in bovine Leydig cells.

The ultrastructural localization of nicotinamide adenine dinucleotide phosphatase (NADPase) in bovine Leydig cells has been studied and compared with the pattern of thiamine pyrophosphatase (TPPase) and acid phosphatase distribution in these cells. Using beta-nicotinamide adenine dinucleotide phosphate (beta-NADP+) as substrate, a marked staining is observed in the intermediate Golgi saccules with some focal extension to the trans aspect. Cisternae on the cis side and associated vesicles yielded only slightly positive reactions. The pattern of NADPase localization is clearly different from that of TPPase which consistently stains only the trans Golgi elements. The specificity of NADPase for its substrate, beta-NADP+, was clearly demonstrated by using substrates modified in either the nicotinamide region e.g. alpha-nicotinamide adenine dinucleotide phosphate (alpha-NADP+), beta-thionicotinamide adenine dinucleotide phosphate (Thio-NADP+), in the attachment site of the monoester phosphate group to the molecule (e.g. 2' monophospho-adenosine 5'-diphosphoribose (ATP-ribose) or adenosine-5-monophosphate (5'AMP). With these substrates only weak or negative reactions were obtained in the Golgi apparatus of the bovine Leydig cell.