Parathyroid Gland Calcium Receptor MRNA Levels Are Unaffected by Chronic Renal Insufficiency or Low Dietary Calcium in Rats

Overview

Journal Endocrine

Specialty Endocrinology

Date 2010 Dec 15

PMID 21153119

Citations 2

Authors

K V Rogers

R L Conklin

S H Lowe

B A Petty

Affiliations

Soon will be listed here.

Abstract

Extracellular ionized calcium (Ca(2+)) is the primary physiological regulator of parathyroid hormone (PTH) secretion and the G protein-coupled receptor (CaR) that mediates this response has been cloned from bovine and human parathyroid glands. The Ca(2+) set-point for the regulation of PTH secretion is right-shifted in primary hyperparathyroidism (1°HPT), but whether there is a similar shift in 2°HPT is unclear. Additionally, the molecular defects associated with such changes in the set-point remain uncharacterized. These experiments were designed to determine (1) if changes in set-point occur in rats with 2°HPT induced by chronic renal insufficiency (CRI) or dietary Ca deficiency, and (2) whether any changes in set-point are mirrored by changes in steady-state mRNA levels for the parathyroid CaR. CaR mRNA levels were quantified in pairs of glands from individual rats using a solution hybridization assay. Blood urea nitrogen and PTH levels were ∼ 4-fold higher in rats with CRI induced by 5/6 nephrectomy 7 weeks earlier. Rats with CRI were also significantly hypocalcemic and hyperphosphatemic. The setpoint was unchanged in CRI rats and CaR mRNA levels were also unaffected. Normal rats fed a 0.02% Ca diet for 6 weeks were markedly hypocalcemic, and had 10- and 15-fold increases in plasma PTH and 1,25-dihydroxyvitamin D(3) levels, respectively. Technical problems prevented assessment of the set-point in these animals, but parathyroid gland CaR mRNA levels were identical in both dietary groups. Thus, neither alterations in mRNA levels for the CaR nor changes in the set-point play demonstrable roles in the pathogenesis of 2°HPT in these models.

Citing Articles

The calcimimetic NPS R-568 decreases plasma PTH in rats with mild and severe renal or dietary secondary hyperparathyroidism.

Fox J, Lowe S, Conklin R, Nemeth E Endocrine. 1999; 10(2):97-103.

PMID: 10451217 DOI: 10.1385/ENDO:10:2:97.

Stimulation of calcitonin secretion by calcium receptor activators: evaluation using a new, highly sensitive, homologous immunoradiometric assay for rat calcitonin.

Lavigne J, Zahradnik R, Conklin R, Lambert L, Logan M, Parihar A Endocrine. 1999; 9(3):293-301.

PMID: 10221596 DOI: 10.1385/ENDO:9:3:293.

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