Parathyroid hormone-1 receptor down-regulation in kidneys from rats with chronic renal failure

Although secondary hyperparathyroidism is a common complication of chronic renal failure, few studies have examined the characteristics of parathyroid hormone (PTH) binding to the kidney or the regulation of the PTH receptor in chronic renal disease, In this study we mea sured PTH binding to the PTH -1 receptor in renal cortical membranes from normal rats and from rats with experimentally induced chronic renal failure, In normal rats, analysis of saturation binding experiments using I-125 PTH-related peptide (chicken, cP THrP) revealed apparent K-d and B-max values of 1.16 +/- 0.14 nmol/l and 33 8 +/- 22.7 fmol/mg, respectively, Three weeks following induction of renal failure there was no change in the affinity of the PTH-1 receptor (K-d = 1. 51 +/- 0.24 nmol/l) but the B-max was reduced by 45% (183 +/- 32.5). In nor mal rats which had undergone thyroparathyroidectomy, the Kd was unchanged ( 1.17 +/- 0.09) while the B-max increased to 459 +/- 31 fmol/mg. We conclude that chronic renal failure is accompanied by a downregulation of renal PTH -1 receptors. Copyright (C) 2001 S.Karger AG, Basel.