Regulation of NaPi-IIa mRNA and transporter protein in chronic renal failure: role of parathyroid hormone (PTH) and dietary phosphate (Pi).

Chronic renal failure (CRF) is associated with a high fractional phosphate excretion (FEPi), secondary hyperparathyroidism, and resistance to parathyroid hormone (PTH). This study was undertaken to characterize the role of PTH and dietary Pi in the regulation of PTH/PTH-related peptide receptor (PTHrP-R) mRNA and NaPi-IIa mRNA and protein in CRF. The following groups of rats were studied: (1) sham-operated (control); (2) CRF: 6 weeks after 5/6 nephrectomy (NPX); (3) NPX and parathyroidectomy (NPX + PTX); (4) NPX rats fed a low-Pi diet (NPX + LP); (5) sham-operated rats fed a low-Pi diet (control + LP); (6) sham-operated after PTX (control + PTX).