Characterization and immunohistochemical localization of nucleoside triphosphate diphosphohydrolase (NTPDase) in pig adrenal glands (presence of a non-sedimentable isoform)

Considering that adrenal glands possess a variety of purinoceptors associat ed with various cell types and that some of these cells (chromaffin cells) secrete large amounts of adenine nucleotides, it was of interest to localiz e nucleoside triphosphate diphosphohydrolase (NTPDase) in these glands and to define the biochemical characteristics of this ectonucleotidase. Immunol ocalization produced a moderate reaction in capsula and medulla, with no si gnal in zona glomerulosa and zona reticularis. In contrast, a very strong r eaction was found in zona fasciculata. Biochemical analysis of particulate fractions isolated from whole glands revealed high levels of ATPase and ADP ase activities. This appeared to be attributable to the NTPDase since the l evel of ADPase was as high as ATPase. Both ATPase and ADPase activities wer e similarly inhibited by sodium azide. Additionally electrophoretograms wit h these two substrates showed comparable patterns. Western blots with 'Ring o', an antibody that recognizes the different isoforms of mammalian NTPDase s, showed the presence of isoforms of NTPDases at 54 and 78 kDa, respective ly. Interestingly, the 54 kDa isoform remains in the supernatant of a chrom affin granule lysate after ultracentrifugation. Up until now little interes t has been given to the relationship between adrenal medulla and cortex. Pr esence of purinoceptors and ectonucleotidases in both these regions togethe r with the effects of ATP in vivo and in vitro in different species indicat e that purines play a significant role in adrenal glands. (C) 2000 Elsevier Science B.V. All rights reserved.