Interspecies comparison of renal cortical receptors for parathyroid hormone and parathyroid hormone-related protein

Abstract

Parathyroid hormone (PTH) and PTH-related proteins (PTHrP) interact with a common receptor in rat bone cells and in canine renal membranes with similar affinity, but PTHrP are substantially less potent than PTH in stimulating adenylate cyclase in canine renal membranes; in contrast, PTH and PTHrP are equipotent in stimulating adenylate cyclase in rat bone cells. This discrepancy has been largely viewed as reflecting differences in the relative efficiency of signal transduction of PTHrP between bone and kidney assay systems. To test the alternative (but not mutually exclusive) hypothesis that these differences could reflect interspecies differences in PTH receptors, we have characterized the bioactivity of amino-terminal PTHrP and PTH in rat and human renal cortical membranes (RCM) and compared them to results we previously reported in canine RCM. The stability of PTH and PTHrP peptides under binding and adenylate cyclase assay conditions was greater than 80% for each species. Competitive inhibition of [125I](Tyr36)hPTHrP-(1-36)NH2 binding to rat RCM by bPTH-(1-34) and (Tyr36)hPTHrP-(1-36)NH2 yielded nearly identical binding dissociation constants (3.7 and 3.6 nM, respectively), and binding to human RCM demonstrated slightly greater potency for PTHrP (0.5 nM) than for PTH (0.9 nM). Similarly, adenylate cyclase stimulating activity was equivalent for the two peptides in rat RCM, but PTHrP was twofold more potent than PTH in human RCM. Covalent photoaffinity labeling of protease-protected rat RCM yielded an apparent 80 kD receptor protein, and cross-linking of human RCM labeled an 85 kD receptor, indistinguishable in size from the canine renal PTH receptor. We conclude that rat, canine, and human renal cortical PTH receptors exhibit species specificity. The previously observed differences between rat bone cells and canine renal membranes in the efficiency of signal transduction by PTHrP may be explained, at least in part, by these species differences.

Quantitative comparison of PTH1R in breast cancer MCF7 and osteosarcoma SaOS‐2 cell lines

“…The results showed distinct differences in both competitive binding studies and labelling affinities studies of PTHrP-1-34 in SaOS-2 and MCF7 cell lines. Interestingly, the Scatchard analysis of the binding data in both cell lines revealed the presence of 4,25,30,38 We focused after this on the differences in binding affinity of PTH and PTHrP in the two cell lines. It has been shown that positions 5 and 23 are critical in conferring specificity for the PTH1R.…”

Cyclic AMP Formation in Rat Bone and Kidney Cells Is Stimulated Equally by Parathyroid Hormone-Related Protein (PTHrP) 1-34 and PTH 1-34*

“…A possible reason for these discrepant results may be the use of heterologous models, with membrane and cell preparations from different species, in earlier studies. This is supported by a recent interspecies comparison of PTH receptors on renal membranes: N-terminal fragments of PTHrP and bovine PTH were equipotent in stimulating adenylate cyclase in membranes from rat and human origin; however, PTHrP was 15-fold less potent in canine membranes (Orloff et al, 1991;Orloff et al, 1989 a). Both peptides had equal binding affinities in all three systems.…”

Intermittent Administration of Human Parathyroid Hormone before Osteosynthesis Stimulates Cancellous Bone Union in Ovariectomized Rats

“…Human PTH [h-PTH (1-34), Asahi Kasei Pharma Co. Ltd., Tokyo, Japan] was dissolved in 0.1 M sodium acetate buffer (PH 7.2) containing 0.1% bovine serum albumin (Seto et al 1999). There is 4 amino-acid differences compared to rat PTH, but the activity or reaction of h-PTH to rat tissue are not different compared to those of rat PTH (Orloff JJ et al 1991). h-PTH (30 µg/ kg body weight) or its vehicle was administered subcutaneously 3 times a week for 2 or 4 weeks based on previous studies (Skripitz and Aspenberg 2001;Komatsubara et al 2005) (Fig.…”