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In rat hepatocytes, the hypertonic activation of Na + conductance and Na + ‐K + ‐2Cl − symport ‐ but not Na + ‐H + antiport ‐ is mediated by protein kinase C
Author(s) -
Heinzinger Heidrun,
Boom Frank,
Tinel Hanna,
Wehner Frank
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00703.x
Subject(s) - symporter , antiporter , chemistry , staurosporine , membrane transport , cotransporter , ion transporter , ouabain , biophysics , phloretin , maleimide , protein kinase c , sodium , biochemistry , membrane , kinase , transporter , biology , organic chemistry , polymer chemistry , gene
1 The initial event in the regulatory volume increase (RVI) of rat hepatocytes is an import of extracellular Na + via Na + conductance, Na + ‐K + ‐2Cl − symport, and Na + ‐H + antiport. 2 Here, the protein kinase inhibitors staurosporine (100 nmol l −1 ) and bis‐indolyl‐maleimide I (400 nmol l −1 ) were used to test for a possible contribution of protein kinase C (PKC) to the hypertonic activation of these transporters in confluent primary cultures. 3 Stimulation of Na + conductance was monitored: (i) by use of a differential approach based on Na + fluxes, (ii) by means of cable analysis, and (iii) in experiments with low Na + pulses. All three experimental protocols in concert demonstrated a block of the activation of Na + conductance by staurosporine and bis‐indolyl‐maleimide I. 4 In addition, both compounds significantly reduced the hypertonic activation of Na + ‐K + ‐2Cl − symport (quantified on the basis of furosemide‐sensitive 86 Rb + uptake) to approximately 30 %. 5 In contrast, neither staurosporine nor bis‐indolyl‐maleimide I had any detectable effect on the hypertonicity‐induced alkalinization of cell pH via Na + ‐H + antiport (determined fluorometrically). 6 Staurosporine and bis‐indolyl‐maleimide I completely blocked the RVI of rat hepatocytes (quantified by means of confocal laser‐scanning microscopy). The high efficiency of the block suggests an additional inhibitory effect of both compounds on the activity of Na + /K + ‐ATPase (determined as ouabain‐sensitive 86 Rb + uptake). 7 It is concluded that the hypertonic activation of rat hepatocyte Na + conductance and Na + ‐K + ‐2Cl − symport ‐ but not Na + ‐H + antiport ‐ is probably mediated by PKC.