It has been demonstrated in humans that the phosphatonin FGF-23 also plays an important regulatory role in the adjustment of blood pressure and renal excretion of sodium (Na): Increased FGF-23 serum levels are positively correlated with Na retention. As demonstrated in mice, high intake of sodium chloride (NaCl) leads to a significant decrease of serum FGF-23 concentrations and consequently of Na retention. The aim of this study was to investigate the effect of high oral NaCl intake on serum FGF-23 and Na concentrations as well as on renal Na excretion in cats.

Eleven healthy adult European short hair cats were fed a balanced control diet (CON) for 28 days (18 d adaption, 10 d balance trial), followed by feeding an above-maintenance level of Na (diet HNaCl; 2.5 g Na/1,000 kcal) by adding NaCl. On the last day of the trial, blood samples were obtained in the fasted animals (pre) and 3 h postprandially (ppr) and analysed for serum FGF23 (sandwich ELISA by KAINOS Laboratories Inc., Tokyo, Japan) and Na (flame photometry). Urine was collected quantitatively during the balance trial, and a pooled sample for each cat was analysed for Na. For statistical evaluation, Student's t-test was applied.

Feeding diet HNaCl caused a significant increase in renal Na excretion (CON: 29.0±4.4; HNaCl: 136.5±25.9 mg/kg BW/d) and a significant postprandial decrease of serum Na concentrations (157±2 vs. 146±4 mmol/l). Pre Na concentrations as well as pre and ppr serum FGF23 concentrations were not affected by NaCl intake.

In contrast to previous findings in other species, neither led high intake of NaCl to decreased serum FGF-23 concentrations nor were serum FGF-23 and Na retention correlated in cats. In alignment with these results, it was previously shown that unlike in humans, feeding high amounts of NaCl does not influence blood pressure in cats. Comparatively low-serum Na levels in trial HNaCl may be due to the significantly increased renal Na excretion. In cats, a high renal Na excretion due to high salt intake does not seem to be controlled by FGF-23 serum concentrations. Therefore, it is hypothesised that in cats regulatory effects of FGF-23 differ from that in other species like humans and mice.

Disclosures

No disclosures to report.