Kidney Specific BMAL1 Knockout Exhibit Sex‐dependent Differences in the Expression and Activity of Renal H, K‐ATPases

Two isoforms of the Hydrogen, Potassium‐ATPases, HKa 1 and HKa 2 , located in the cortical collecting duct (CCD) are important in acid‐base regulation and potassium handling and are encoded by ATP4a and ATP12a, respectively. Elabida et al. has reported that progesterone mediates antikaliuretic effects via stimulation of HKa 2 expression. The circadian clock influences kaliuresis as demonstrated by its 24‐hour cycles. Therefore, the objective of this study was to determine whether expression of the clock gene BMAL1 affected HK activity and if there was a difference in females compared to males. Kidney‐specific BMAL1 knockout mice (KO) were generated using floxed exon 8 BMAL1 mice crossed with kidney‐specific cadherin Cre+ mice. Floxed Cre− littermates were used as control mice (CNTL). Kidneys were collected for qPCR or CCD isolation. HK‐mediated H secretion in isolated perfused CCD was measured as EIPA‐ and bafilomycin A 1 ‐insensitive intracellular pH (pH i ) recovery from an acute H loading (NH 4 ) using BCECF. pHi recovery was measured in A‐ and B‐type intercalated cells (IC) from female and male mice. IC type were differentiated based on the pH i response to peritubular Cl removal. Female mice had 2.3 fold greater ATP12a mRNA in the cortex than males (P SEX =0.008; N=4–6) and greater cortical ATP4a mRNA than males (1.5 fold; P SEX <0.0001), however, there was no genotype difference. Furthermore, the expression of BMAL1 affected ATP4a expression in a sex‐dependent manner (P SEX*KO =0.02). Overall, ICs from female mice exhibited faster rates of HK‐mediated H flux than males (4.3 ± 0.5 vs. 2.9 ± 0.3 H/min, P SEX <0.02, N IC/CCD =108/11 & 103/10). We observed a heterogeneous IC cell population with the number of A‐type ICs increasing (and B‐cells decreasing) from the outer to the inner CCD (P<0.001). We systematically analyzed HK activity in A‐ & B‐type ICs from the outer to the inner CCD. Female KO mice had 2.5 fold greater HK activity than female CNTL in A‐type ICs from mid and inner CCD (2.8 ± 0.6 vs. 6.9 ± 1.0, N=23/4 & 23/4, P KO <0.001). In conclusion, these data demonstrated a sex‐dependent difference in mRNA expression and HK activity. HKa 1 and HKa 2 mRNA expression and HK activity in females are greater than in males. HK activity is upregulated in the acid secreting ICs in female BMAL1 KO mice compared with controls. The clock gene BMAL1 has a sex‐specific role in regulating cortical mRNA expression of HKa 1 and HK‐activity. Support or Funding Information 5T32HL083810‐10 NIH/NIDDK 1R01DK109570 The Gatorade Trust through the UF Department of Medicine This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .