Figure 3.

UDCA inhibits OATP4A1 but does not cause transstimulation, suggesting it is not transported. A) ³H-ES uptake into oocytes by OATP4A1 was shown to be linear up to 10 min, and this was inhibited by cold 2.5 mM ES (n = 5 ovaries, 5 oocytes per condition). B) ³H-ES uptake (under sodium-free conditions) in OATP4A1-injected oocytes was inhibited by 500 μM ES, TC, and UDCA (*P < 0.05, n = 5 ovaries, 5 oocytes/condition), but not by negative control glycine. Data are presented as means and sem and are analyzed by a 1-way ANOVA with Dunnett’s post hoc (compared with ³H-ES alone). C) ³H-ES efflux in OATP4A1-injected oocytes is transstimulated by ES (*P < 0.05, n = 3) and TC (**P < 0.01), but not by UDCA or negative control glycine. This suggests that UDCA is not a substrate of OATP4A1. Data are adjusted for background water-injected responses and presented as means and sem. Data were analyzed by a 1-way ANOVA with Dunnett’s post hoc (compared with buffer alone); n > 3 individual ovaries, 5 oocytes per condition for uptake, 15 oocytes/condition for efflux.