ISSN:
1573-4919
Keywords:
Na-selective microelectrode
;
bumetanide
;
ouabain
;
heart cells
;
membrane potentials
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Abstract We have recently reported the presence of an electroneutral (Na + K + 2 Cl) cotransport mechanism that is bumetanide-sensitive and maintains Cli above its electrochemical equilibrium in cultured chick heart cells. In steady state, (Na + K + 2 Cl) cotransport is inwardly directed and so contributes to the Na influx that must be counterbalanced by the activity of the Na/K pump to maintain Nai homeostasis. We now show that manipulating (Na + K + 2 Cl) cotransport by restoring Clo to a Cl-free solution indirectly influences Na/K pump activity because the bumetanide-sensitive recovery of a infNa supi to its control level and the accompanying hyperpolarization could be blocked by 10−4M ouabain. In another protocol, when the Na/K pump was reactivated by restoring Ko (from 0.5 mM to 5.4 mM) and removing ouabain, the recovery of aNa was attenuated by 10−4M bumetanide. The relatively slow rate of ouabain dissociation coupled with the activation of Na influx by (Na + K + 2 Cl) cotransport clearly establishes the interaction of these transport mechanisms in regulating Nai. Although (Na + K + 2 Cl) cotransport is electroneutral, secondary consequences of its activity can indirectly affect the electrophysiological properties of cardiac cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00220767
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