Endogenous and exogenous citrate transport and release in prostatic preparations: Semi-polarized two-dimensional cultures of human PNT2-C2 cells and isolated tubules and segments of rat prostate

BACKGROUND. Electrophysiological characterization of normal human prostate epithelial cells showed exogenous trivalent citrate transport (release) to be K⁺-dependent. METHODS. (1) Ussing chamber recordings of short circuit current (SCC) were used to study citrate transport in the same (PNT2-C2) cell line grown on micro-pore filters as a monolayer. (2) Release of endogenous citrate from confluent cultures and tubules and segments of rat prostate was measured using a fluorescence technique. (3) Enzyme-spectrophotometry was employed to detect citrate release from segments of rat prostate. RESULTS. Citrate transport across the PNT2-C2 monolayer was asymmetrical, consistent with release into the lumen-side. Fluorescence and/or enzyme-spectrophotometric measurements showed that time-dependent citrate release (endogeneous and preabsorbed) occurred from rat prostate (tubules and segments), but not kidney or lung. The release was dependent on extracellular K⁺ but not Na⁺. CONCLUSIONS. Citrate release from prostatic cells and tissues (rat and human) was K⁺-dependent, consistent with the previous electrophysiological data.