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This study investigated the effects of partial Na pump inhibition and Na-H exchange inhibition on contractile function, intracellular pH (pHi), and intracellular Ca concentration ([Ca]i) during intracellular acidosis, using the fluorescent dyes 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein and fura-2 in isolated cardiac cells of adult rabbits. Intracellular acidosis with normal extracellular pH was induced by an NH4Cl (10 mM) prepulse technique. A nontoxic concentration (0.5 microM) of ouabain was used to inhibit the Na pump. 5-(N-ethyl-N-isopropyl)amiloride (EIPA) was used to inhibit Na-H exchange. In both the absence and presence of ouabain, pHi fell transiently and then recovered after removal of NH4Cl. Ouabain did not alter the pHi changes observed after removal of NH4Cl. Diastolic and systolic [Ca]i increased during acidosis after NH4Cl removal. In the presence of ouabain, the increase in [Ca]i during acidosis was greater than that in the absence of this drug. Ouabain enhanced the recovery of contractile function during acidosis. In both the absence and presence of ouabain, Na-H exchange inhibition by EIPA reduced the recovery of pHi and mechanical function and the increase in [Ca]i, which were normally observed after NH4Cl removal. These data suggest that in adult rabbit myocytes the Na pump inhibition enhances the increase in [Ca]i during acidosis, and the Na-H exchange inhibition reduces it. The [Ca]i increase during acidosis may be in part due to the altered Na-Ca exchange, which in turn results from the increased Na-H exchange.
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
February 1987,
Circulation research,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
January 2002,
Pharmacological research,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
March 1995,
The American journal of physiology,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
August 1994,
Biochemical and biophysical research communications,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
April 1994,
Pulmonary pharmacology,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
March 1997,
Methods and findings in experimental and clinical pharmacology,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
June 2000,
Circulation,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
July 1999,
Biophysical journal,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
April 1996,
Annals of the New York Academy of Sciences,
T Nakanishi, and
M Seguchi, and
T Tsuchiya, and
E J Cragoe, and
A Takao, and
K Momma
January 1985,
Advances in myocardiology,
