Effects of lowering food intake by high phosphorus diet on parathyroid hormone actions and kidney mineral concentration in rats

We investigated whether lowering food intake by high phosphorus (P) diet influenced parathyroid hormone (PTH) actions, bone turnover markers, and kidney mineral concentration in rats. Rats in two of the three groups were respectively given free access to a control diet (C group) and a high P diet (HP group) for 21 days. Rats in another group (PF group) were pair-fed the control diet with the HP group. Compared to the C and PF groups, serum PTH concentration, urinary C-terminal telopeptide of type I collagen excretion, and kidney calcium and P concentrations were significantly higher in the HP group. Urinary excretion of cAMP was significantly lower in the HP group than in the C and PF groups. These results suggested that high P diet decreased PTH action in the kidney and increased bone resorption and kidney mineral concentrations independently of lowering food intake.