Response of NaSuperscript+/Superscriptdepende

Authors: Alessandra Pagliarani Patrizia Bandiera Vittoria Ventrella Fabiana Trombetti Maria Pia Manuzzi Maurizio Pirini Anna Rosa Borgatti

Publish Date: 2008/01/04

Volume: 55, Issue: 1, Pages: 49-56

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Abstract

In vivo and in vitro experiments elicited different responses to ammonia nitrogen ammoniaN of gill and mantle NaKATPase and ouabaininsensitive NaATPase activities in the Philippine clam Tapes philippinarum Shortterm 120 h exposed clams to sublethal ammoniaN NH3+NH 4 + concentrations 15 and 30 mg/L ammoniaN showed enhanced gill and mantle ouabaininsensitive ATPase activity and decreased mantle NaKATPase activity with respect to unexposed clams while gill NaKATPase was unaffectedIn vitro experiments showed that NH 4 + could efficiently replace Na+ in ouabaininsensitive ATPase activation and K+ but not Na+ in Na KATPase activation Simple saturation kinetics was constantly followed with similar K 05 values to that of the substituted cation The same maximal ouabaininsensitive ATPase activation was obtained at 80 mM Na+ or NH 4 + in the gills and at 50 mM Na+ or NH 4 + in the mantle and that of NaKATPase at 10 mM K+ or NH 4 + in the presence of 100 mM Na+ in both tissues The two coexistent ATPase activities maintained their typical response to ouabain also when stimulated by NH 4 + when activated by Na++K+ or by Na++NH 4 + the ATPase activity was completely suppressed by 10−3 M ouabain whereas the Na+ or NH 4 + stimulated ATPase activity was unaffected by up to 10−2 M ouabain

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