Modulation of phosphate accumulation in isolated chick kidney cells by gluconeogenic substrates

An isolated proximal-tubule preparation is described that accumulates Pi in a saturatable, Na+-dependent manner. The initial rate of Pi accumulation is greater in cells incubated with the gluconeogenic substrates pyruvate and lactate than in cells incubated with glucose. Glucose was produced from the substrates under these conditions. Incubation with either NAD+ or NADH inhibits the initial rate of Pi accumulation. These data provide evidence that the effects of gluconeogenesis on Pi uptake are not mediated by the oxidation state of the nicotinamide coenzymes.