(M1430-05-31) Effects of Testosterone on Kidney Monocarboxylate Transporter Expression

Purpose: Proton- and sodium- dependent monocarboxylate transporters (MCTs and SMCTs) utilize a secondary active transport mechanism to mediate the flux of short-chain fatty acids, l-lactate, butyrate and xenobiotic substrates (1). Tissue distribution is widespread with kidney expression of interest to urinary drug excretion. MCT1, MCT4 and SMCT1 are expressed in renal cells with CD147 (basigin) as the ancillary protein for MCTs 1 and 4 (1). Previous studies in our laboratory quantified renal mRNA and whole cell and membrane expression in intact and castrated males, ovariectomized females, and females in the four estrous cycle stages with results demonstrating sex hormone mediated regulation (2). The role of androgens is further investigated herein via the quantification of kidney MCT1, MCT4, CD147 and SMCT1 mRNA and membrane expression in castrated (CST) and ovariectomized (OVX) Sprague-Dawley rats implanted with testosterone or corresponding placebo.

Methods: 10 week old castrated (CST) male, ovariectomized (OVX) female and intact male and female Sprague-Dawley rats (Charles River) were subcutaneously implanted with 7.5 mg testosterone or corresponding placebo 60-day release pellets. Kidneys were collected after 21 days of hormone treatment. Soluble and membrane protein was isolated with ProteoExtract Native Membrane Protein Extract Kit (Sigma-Aldrich) and total protein concentration was measured with bicinchoninic acid (BCA) assay. Renal MCT1, MCT4, CD147 and SMCT1 membrane expression normalized to total lane was quantified with western blot. PureLink RNA Mini Kit (Thermo Fisher Scientific) was utilized to extract total RNA and mRNA was measured with qPCR.

Results: No significant difference in MCT1, MCT4, CD147 and SMCT1 mRNA expression was observed among CST testosterone and CST placebo groups and among OVX testosterone and OVX placebo groups. MCT1 membrane expression was significantly greater in OVX testosterone group compared to OVX placebo group (p=0.0316). Intact males had significantly lower MCT1 membrane expression compared to testosterone treated CST (p=0.042) and OVX (p=0.0185) groups. MCT4 membrane expression was significantly lower in intact males compared to CST testosterone group with p< 0.0001. SMCT1 membrane expression was significantly lower in CST testosterone group compared to CST testosterone placebo (p=0.0008). Intact males expressed significantly lower SMCT1 membrane protein than OVX testosterone group (p=0.0007).

Conclusion: The results demonstrate testosterone mediated regulation of monocarboxylate transporter membrane expression. Future studies will evaluate the implications of this hormone-mediated regulation on the renal clearance of MCT/SMCT substrates.

References: 1. Felmlee MA, Jones RS, Rodriguez-Cruz V, Follman KE, Morris ME. Monocarboxylate Transporters (SLC16): Function, Regulation, and Role in Health and Disease. Pharmacol Rev. 2020;72(2):466-85.
2. Wei H, Cao J, Fallert T, Yeo S, Felmlee M. GHB Toxicokinetics and Renal Monocarboxylate Transporter Expression are Influenced by the Estrus Cycle in Rats2022.

Acknowledgements: Funding for this project provided by NIDA/NIGMS DA052120