(W0930-05-33) Regulation of Rat Hepatic Monocarboxylate Transporter Expression by Sex and Cross-Sex Hormone Treatment

Purpose: Our objective is to quantify hepatic MCT1, MCT4, and CD147 membrane protein expression in rats treated with sex or cross-sex hormone therapy.

Methods: Male and female Sprague Dawley (SD) rats, ovariectomized (OVX) females, and castrated (CST) males were obtained from Charles River at 8 weeks of age and were housed in a temperature-controlled room with a 12-hour day/night lighting cycle. At 10 weeks of age, OVX female and CST male SD rats were implanted subcutaneously with 60-day release pellets containing 1.5 mg estrogen and/or 50 mg progesterone or 7.5mg testosterone or their corresponding control pellets (Innovative Research of America) (N = 6/treatment group). Following euthanasia, livers were harvested. Membrane-bound protein was extracted from the liver using a ProteoExtract Native Membrane Extraction kit. Na⁺/K⁺ ATPase expression was evaluated by western blot to verify membrane isolation. MCT1, MCT4, and CD147 protein expression levels were quantified by western blot and normalized to total lane expression.

Results: Intact females showed significantly lower MCT1 protein levels when compared with intact males. CST males with estrogen treatment significantly reduced MCT1 protein expression when compared to the corresponding placebo group. Compared to combo placebo groups, both OVX and CST animals treated with female combo sex hormones showed significantly decreased MCT1 protein levels. With the treatment of testosterone, significantly higher MCT1 protein expression was observed in both OVX and CST animals when compared with intact males and females. For MCT4, intact females showed significantly higher protein expression than intact males. A significant reduction of MCT4 protein was observed in OVX females treated with progesterone compared to its placebo group. Interestingly, CST males with combo treatment showed a significant increase in MCT4 compared to the placebo group. >Compared to intact females, OVX females with estrogen treatment significantly lowered CD147 expression. The treatment of progesterone in OVX animals exhibited a reduction in CD147 when compared to intact males and females.

Conclusion: MCT1, MCT4 and CD147 localized on the liver are regulated by sex and cross sex hormone treatment. These results suggest that hepatic MCT regulation is not dependent on biological sex, but dependent on exposure to sex hormones. Alterations in liver membrane protein expression may affect the hepatic drug disposition and elimination of monocarboxylate transporter substrates

Acknowledgements: This work is funded by NIDA/NIGMS DA052120.

Figure 1. MCT1 membrane protein expression in liver isolated from Sprague–Dawley rats. Results are presented as mean ± SD, N = 6. ap < 0.05 compared to female(estrus) group; bp < 0.05 compared to male group; cp < 0.05 compared to OVX combo placebo group; dp < 0.05 compared to CST estrogen placebo group; ep < 0.05 compared to CST combo group.

Figure 2. MCT4 membrane protein expression in liver isolated from Sprague–Dawley rats. Results are presented as mean ± SD, N = 6. ap < 0.05 compared to female(estrus) group; bp < 0.05 compared to male group; cp < 0.05 compared to OVX combo placebo group; ep < 0.05 compared to CST combo group; fp < 0.05 compared to OVX progesterone group.

Figure 3. CD147 membrane protein expression in liver isolated from Sprague–Dawley rats. Results are presented as mean ± SD, N = 6. ap < 0.05 compared to female(estrus) group; bp < 0.05 compared to male group.