Further insights into sinusoidal organic anion uptake

✍ Scribed by Jorge J. Gumucio; Richard H. Moseley

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 274 KB
• Volume: 15
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.1840150127

✦ Synopsis

Previous studies in cultured rat hepatocytes revealed that initial uptake of sulfobromophthalein (BSP) was markedly reduced upon removal of C1from the medium. In the present study, unidirectional C1gradients were established in short-term cultured rat hepatocytes and their effect on BSP uptake was determined. These investigations revealed that BSP uptake requires external C1-and is not stimulated by unidirectional C1gradients, suggesting that BSP transport is not coupled to C1transport. In contrast, BSP transport is stimulated by an inside-to-outside OHgradient, consistent with OHexchange or H + cotransport. As the presence of C1is essential for but not directly coupled to BSP transport, binding of 3SS-BSP to hepatocytes was determined at 4" C. This revealed an -10-fold higher affinity of cells for BSP in the presence as compared to the absence of C1-(K, + 3.2 f 0.8 vs. 0.42 k 0.09 pM-'; P < 0.02).

Affinity of BSP for albumin was C1--independent, and was -10% of its affinity for cells in the presence of C1-. These results indicate that extracellular C1modulates the affinity of BSP for its hepatocyte transporter.