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The effect of external Ca2+ on p-aminohippurate (PAH) transport was examined using rat kidney cortical slices. External Ca2+ increased the initial rate of PAH uptake, markedly enhanced its maximal accumulation at steady-state conditions and depressed the efflux. Kinetic studies revealed that increasing external Ca2+ from 0 to 2.5 mM resulted in an increase in the Vmax of transport, while the apparent Km values remained constant. When the intracellular Na+ levels of the slices were equal, PAH accumulation was increased in the presence of Ca2+. A divalent cation such as Ba2+, Mn2+ or Sr2+ enhanced PAH accumulation to at least the same degree as Ca2+. While Mg2+ had no effect, La3+ exhibited a little stimulatory effect on the PAH accumulation. We suggest that the stimulatory action of Ca2+ on PAH accumulation is in part dissociated from that of Na+ gradient and that Ca2+ can be substituted by Ba2+, Mn2+ and Sr2+ with regard to the stimulation of PAH accumulation.
Y Matsushima, and
M Gemba
August 1987,
Archives internationales de pharmacodynamie et de therapie,
Y Matsushima, and
M Gemba
December 1981,
Japanese journal of pharmacology,
Y Matsushima, and
M Gemba
May 1986,
The American journal of physiology,
Y Matsushima, and
M Gemba
July 1982,
British journal of pharmacology,
Y Matsushima, and
M Gemba
May 1986,
Research communications in chemical pathology and pharmacology,
Y Matsushima, and
M Gemba
September 1979,
Biochimica et biophysica acta,
Y Matsushima, and
M Gemba
August 1973,
Experientia,
Y Matsushima, and
M Gemba
December 1976,
The Journal of pharmacology and experimental therapeutics,
Y Matsushima, and
M Gemba
April 1950,
The American journal of physiology,
Y Matsushima, and
M Gemba
January 1982,
Renal physiology,
