Reduced salt intake partially restores the circadian rhythm of bladder clock genes in Dahl salt-sensitive rats

Abstract

Aims: To examine the circadian expression changes in bladder clock genes in Dahl salt-sensitive rats following high salt intake.

Main methods: Eighteen rats were divided into three groups: the high-salt diet group (HS group), the normal-salt diet group (NS group), and the salt-load interruption group (from a 4 % salt diet to a normal diet; salt-load interruption group [SI group]). Each rat was placed in an individual metabolic cage for 24 h twice weekly. Water intake, urine production, voiding frequency, and voided volume per micturition were recorded. Furthermore, 108 control rats were prepared. Bladders were harvested every 4 h at six time points. Furthermore, the mRNA expression of clock genes and mechanosensors was analyzed.

Key findings: In the HS group, the bladder clock genes showed lower mRNA levels than in the NS group. The amplitude of circadian expression changes in bladder clock genes in the HS group was lower than that in the NS group. However, after changing from a 4 % salt diet to a normal diet, the waveforms of the clock gene expression in the SI group were closer to those of the NS group. The 24-h water intake and urinary volume of the SI group decreased to levels comparable to those of the NS group.

Significance: Reduced salt intake partially restored the circadian rhythms of bladder clock genes.

Keywords: Circadian rhythm; Clock gene; Inbred Dahl rats; Nocturia; Polyuria.