ULTRACYTOCHEMICAL LOCALIZATION OF OUABAIN-SENSITIVE, POTASSIUM-DEPENDENT P-NITROPHENYLPHOSPHATASE ACTIVITY IN THE GUINEA PIG RETINA

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Abstract
Ouabain-sensitive, K-dependent p-nitrophenylphosphatase activity was studied cytochemically in photoreceptor cells of the normal adult guinea pig retina with a newly developed 1 step lead citrate method (Mayahara, et al. In guinea pig photoreceptor cells fixed for 5 min in a mixture of 2% paraformaldehyde and 0.25% glutalaldehyde, electron dense reaction products were observed on plasma membranes of the inner segments and more proximal portion, but not on membranes of the outer segments. The most intensive reaction products were evident in the pre-synaptic membranes in the outer plexifrom layer. This activity was positive on the apical villi of the Mueller cells, which were spread out distal to the outer limiting membrane into interstices between the inner segments. This reaction was almost completely abolished by 10 mM ouabain or elimination of K. This activity was substrate-dependent and completely inhibited by PCMB- S [p-chloromercuribenzoates] or preheating. In contrast to K-dependent p-nitrophenylphosphatase activity, Mg-ATPase and non-specific alkaline phosphatase activity were not observed on every part of the plasma membranes of the photoreceptor cells.