Abstract
Summary
The divalent cation ionophore A23187 was found to increase glucose production from α-ketoglutarate, glutamine, succinate, and lactate, but not from glycerol in isolated rat renal cortical tubules at external Ca2+ concentrations of 0.1 mM. At an external Ca2+ concentration of 1.0 mM or in the absence of external Ca2+, the ionophore did not increase glucose production from α-ketoglutarate. Ionophore A23187 did not increase cyclic AMP levels in renal cortical tubules. The increase in glucose production produced by ionophore A23187 was completely prevented by preincubation of the tubules with 10-5 M pentobarbital, a known inhibitor of calcium transport in biological systems. The experiments suggest that ionophore A23187 increases gluconeogenesis from a variety of substrates by altering the levels of cytosolic calcium without affecting the concentrations of cyclic AMP.
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