Characterization of dietary and hormonal influences on renal sodium transporters in rodent models demonstrates changes in thick ascending limb and distal tubule expression and localization. — 31a — Evelyn Chan, Jenna Zimmerman, Arooba Ilyas, Karla Otterpohl, Abigail Klein, Tricia Larsen, Michelle Baack

Within kidneys, a diverse array of renal epithelial cells works to maintain electrolyte and water balance to regulate blood pressure and pH. These cells contain varying types of sodium transporters that adjust sodium reabsorption according to the body’s needs. Previous studies have observed sex specific differences in renal sodium transporter regulation, which are thought to optimize reproduction in females. In this study, we performed high resolution microscopy and detailed characterization of nephron-segment specific expression and localization of major sodium transporters and channels in rodents in response to dietary and hormonal influences. Specifically, we examined the impact of varying salt diets in male and female mouse models, as well as effects of pregnancy in female rat models. Furthermore, we characterized sodium transporters and channels in conditional knockout mouse models of actin-associated nonmuscle myosin II A (Myh9). The characterized proteins include: thick ascending limb specific sodium-potassium-chloride cotransporter 2 (NKCC2), distal convoluted tubule specific phosphorylated sodium-chloride cotransporter (pNCC), and cortical collecting duct specific epithelial sodium channel’s gamma subunit (ENaC-γ). Kidney sections underwent multiplex immunofluorescence protein staining and were subjected to confocal microscopy. In addition, western blots of whole kidney lysates were performed in the mouse diet studies to assess protein expression. In low salt diets for both sexes, we observed a slight decrease in NKCC2 and a notable increase in pNCC expression. In high salt diets, decreases in NKCC2 and pNCC expression were demonstrated in both sexes. Moreover, we also confirmed inherent differences between sexes in the extent at which sodium transporter expression was regulated. Pregnant female rats were observed to have decreased NKCC2 expression and undetectable levels of pNCC expression as compared to non-pregnant rats. The results of this project will contribute to our understanding of sexual dimorphism within the regulation of renal sodium transporters and guide future studies.

Sanford Research
Indra Chandrasekar