S. Thirion et al., CYTOCHEMICAL-LOCALIZATION OF ECTO-ATPASES IN RAT NEUROHYPOPHYSIS, The Journal of histochemistry and cytochemistry, 44(2), 1996, pp. 103-111
We studied the distribution of Ca2+- or Mg2+-dependent ATP-ase activit
y in rat neurohypophysis using the lead cytochemical method of Ando et
al. In electron microscopy, precipitates were found lining the outer
surface of the plasma membrane surrounding nerve endings and pituicyte
s. These precipitates were believed to represent the activity of ecto-
ATPases (as opposed to Ca pump ATPases) for the following reasons: the
re was equal activation by Ca2+ in the absence of Mg2+ or Mg2+ in the
absence of Ca2+; the effects of the two ions were not additive; there
was activation by ATP or GTP; and there was resistance to glutaraldehy
de fixation, to high (10 mM) Ca2+ concentrations, and to various inhib
itors such as NEM, vanadate, oligomycin, quercetin, p-chloromercuriben
zoate, ouabain, and levamisole. Cytosolic activity observed in certain
nerve endings in the same conditions of incubation but more sensitive
to NEM is also described and discussed.