Na+, K+-ATPase and ouabain binding activities of chick embryo dorsal root ganglia supported by and deprived of nerve growth factor

✍ Scribed by Stephen D. Skaper; Silvio Varon

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 578 KB
• Volume: 6
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.490060113

✦ Synopsis

Abstract

Recently we have shown that nerve growth factor (NGF) influences the coupled movements of Na^+^ and K^+^ across the membrane of chick embryo dorsal root ganglion (DRG) and other target cells. These ionic effects of NGF are consistent with a model in which NGF acts through the classical Na^+^,K^+^‐ATPase pump. Direct evidence for NGF‐induced alteration of this pump has been sought in the present study through two approaches. In one approach, DRG cell dissociates were incubated for 6 hours without NGF (to allow development of the ionic defect), and [^3^H]ouabain binding to the cells was measured before and during a delayed administration of NGF. No differences were detected in either total binding or binding time. In the second approach, intact DRG or DRG dissociates were incubated for 6 hours with or without NGF, or received NGF after 6 hours of deprivation, and Na^+^,K^+^‐ATPase (ouabain‐sensitive) activity was measured in the corresponding microsomal preparations. Activity levels were found to be the same in all cases, and were unchanged by addition of NGF directly to the enzyme preparations. Different concentrations of Na^+^, K^+^, or ATP affected in identical manners the enzyme preparations from NGF‐treated and NGF‐deprived ganglia, speaking against NGF‐imposed changes in the affinities of the corresponding enzyme sites. Also unsuccessful were attempts to reveal NGF‐related differences by testing ouabain‐sensitive ATPase activity (1) in the presence of varying concentrations of cyclic AMP or of Ca^2+^, (2) after treatment with Triton X‐‐100 or in the presence of vanadate, or (3) on addition of a 100,000g DRG extract. These negative findings are discussed in terms of the Na^+^,K^+^‐ATPase hypothesis for NGF action.