Abstract
The anti-diuretic hormone arginine vasopressin is thought to be a detrimental factor in polycystic kidney disease (PKD). We previously reported that high water intake (HWI) reduced urine osmolality and urinary arginine vasopressin, improved renal function, and reduced the kidney/body weight ratio in PCK rats, an orthologous model of human PKD. In PKD patients, however, it is reported that HWI increases total kidney volume, urine volume, and urine sodium excretion, which could be a consequence of high salt intake. In the current study, we loaded PCK rats with high salt concurrently with HWI to determine whether this human-imitated condition exacerbates disease progression. PCK rats were assigned into 4 groups: control group (CONT: distilled water), HWI group (HWI: 5% glucose in water), HWI with 0.2% NaCl group (HWI+0.2%NaCl), and HWI with 0.45% NaCl group (HWI+0.45%NaCl). Total water intake during the experimental period was increased by 1.86-, 2.02-, and 2.42-fold in HWI, HWI+0.2%NaCl, and HWI+0.45%NaCl, and sodium intake was increased by 2.55- and 5.83-fold in HWI+0.2%NaCl and HWI+0.45%NaCl, respectively, compared with CONT. Systolic blood pressure was higher in HWI+0.2%NaCl and HWI+0.45%NaCl than in both CONT and HWI. Serum urea nitrogen, kidney/body weight ratio, cAMP, cystic area, and fibrosis index were significantly lower in HWI compared with CONT, and these ameliorative effects were not abrogated in either HWI+0.2%NaCl or HWI+0.45%NaCl. The amount of sodium excreted into the urine was increased by 2.50- and 8.38-fold in HWI+0.2%NaCl and HWI+0.45%NaCl, respectively, compared with HWI. Serum sodium levels were not different between the groups. These findings indicate that the beneficial effect of HWI against the progression of cystic kidney disease was not affected even by high salt-overload in this rodent model of PKD.
Highlights
Polycystic kidney disease (PKD) is the most common hereditary renal disorder with countless cysts in bilateral kidneys
We previously reported that high water intake (HWI) reduced urine osmolality and urinary arginine vasopressin, improved renal function, and reduced the kidney/body weight ratio in PCK rats, an orthologous model of human polycystic kidney disease (PKD)
We previously reported that high water intake (HWI) via enhanced hydration by adding 5% glucose to drinking water had an inhibitory effect on the progression of PKD with reduced urine osmolality and urinary Arginine vasopressin (AVP) in PCK rats, a human gene orthologous model of autosomal recessive PKD [14]
Summary
Polycystic kidney disease (PKD) is the most common hereditary renal disorder with countless cysts in bilateral kidneys. We previously reported that high water intake (HWI) via enhanced hydration by adding 5% glucose to drinking water had an inhibitory effect on the progression of PKD with reduced urine osmolality and urinary AVP in PCK rats, a human gene orthologous model of autosomal recessive PKD [14]. In that case, increased urine sodium excretion was observed, which could possibly be the consequence of primary high salt intake, probably because if the patients did not increase their sodium intake, the plasma sodium level may be reduced inappropriately by HWI. This clinical outcome suggests that increased salt intake may cause the deterioration of symptoms in PKD patients. In this study, in order to determine whether increased salt intake attenuates the ameliorative effect of HWI, we loaded PCK rats with high sodium chloride (NaCl) concurrently with HWI
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