Evidence for two aspartate transport systems in prostate epithelial cells

Abstract

The transport of aspartate was measured in isolated prostate cells. Two kinetically distinct uptake systems of high (K(m) = 10.0 μM) and low (K(m) = 0.8 mM) affinity were observed. Transport by both systems was Na± dependent and saturable. The tissue distribution of aspartate was also determined by measuring the washout kinetics of endogenous and radio-labeled aspartate from prostate fragments. The distribution of aspartate resulted in 47% of aspartate in the intracellular compartment and 52% in the extracellular (presumably) lumenal compartment. The distribution of aspartate resulted in a calculated intracellular to plasma concentration gradient of approximately 43. We concluded that prostate cells maintain a considerable intracellular to plasma gradient for aspartate and that these cells contain a transport mechanism capable of uptake of aspartate against this considerable gradient.