The influence of heavy metal ions, spermine and sodium nitroprusside on ATP-hydrolases of cell membranes of rat colon smooth muscle.

A A Kaplia

doi:10.15407/ubj88.04.020

Abstract

The specific features of functional lability of the rat colon smooth muscle (CSM) АТР-hydrolases were studied. Na+,K+-AТРase activity is effectively inhibited by divalent ions of both transition (≥ 0,1 µM) and nontransition (≥ 1 µM) heavy metals in succession by efficiency: Cu2+ > Fe2+ ≥ Cd2+ (10 µM). Polyamine spermine (0,5-1,0 mM) is a weak Na+,K+-AТРase inhibitor at saturation concentrations of ions and substrate. Sodium nitroprusside (1 mM) as nitric oxide-generating compound exhibits weak Na+,K+-AТРase inhibition only after prolonged preincubation with membranes. Mg2+-АТР-hydrolase activity in all cases is much more resistant to studied agents. Considering the example of the CSM Na+,K+-AТРase it is assumed that enzyme has specific biochemical features that contribute to its role as a potential target and redox-sensor, mediating the pathological mechanisms of heavy metal intoxication and cell oxidative damage.

Highlights

N a+,K+-АТPase (EC 3.6.1.37) is a fundamental enzyme of the ion homeostasis regulation by providing energy-dependent electrogenic contradirectional transport of Na+ and K+ across plasma membrane of animal cells to maintain electrochemical gradient of monovalent ions, membrane potential, electrical excitability and associa ted processes of transport of ions and metabolites [1]
Being the main consumer of the ATP energy, synthesis of which requires 20-80% of the oxygen consumed by mammalian cell, Na+,K+-АТPase is believed to be involved into pathophysiological responses under oxidative stress, ischemia-hypoxia, mitochondrial dysfunction, reprogramming of the oxidative metabolism pathways, etc [4,5,6]
It is important to ascertain the biochemical properties of this enzyme in comparison with ATP-hydrolases not belonging to P-type family to evaluate the expected sarcolemmal targets participating in impairment of the smooth muscle motility of this intestine region

Summary

Introduction

N a+,K+-АТPase (EC 3.6.1.37) is a fundamental enzyme of the ion homeostasis regulation by providing energy-dependent electrogenic contradirectional transport of Na+ and K+ across plasma membrane of animal cells to maintain electrochemical gradient of monovalent ions, membrane potential, electrical excitability and associa ted processes of transport of ions and metabolites [1]. Chronic iron overload disorders (hemochromatosis, chronic drug or dietary intoxication) can be an aggravating factor of the pathogenesis, associated with accumulation of extremely toxic iron pool not linked to transferrin or ferritin in the plasma or inside the cell, respectively. It may cause the redox imbalance in tissues and entail cellular damage both at plasma membrane level and intracellularly. The aim of this study is to comparatively examine the sensitivity of the ATP-hydrolases (namely Na+,K+-ATPase and Mg2+-АТРase) of rat CSM cellular membranes to divalent transition and nontransition metal ions and to evaluate the inhibitory potency of polyamine spermine and nitric oxidegenerating compound sodium nitroprusside for these enzymatic systems

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