In Reply to ‘Dialysate Calcium Concentration and Mineral Metabolism in Long and Long-Frequent Hemodialysis’

N-methyl-d-aspartate receptors (NMDAR) are tetrameric amino acid receptors which act as membrane calcium channels. The presence of the receptor has been detected in the principal organs responsible for calcium homeostasis (kidney and bone), pointing to a possible role in mineral metabolism. In the present work, the presence of the receptor was determined in normal parathyroid glands (PTG) by real-time PCR, immunoprecipitation, and immunohistrochemistry. Healthy animals showed a decrease in blood parathyroid hormone (PTH) levels 15 min after the treatment with NMDA. This effect was also observed in animals with high levels of PTH-induced EDTA injection, but not in uremic animals with secondary hyperparathyroidism (2HPT). Normal rat PTG incubated in media with low calcium concentration (0.8 mM CaCl2) showed a decrease in PTH release when NMDA was added to the media. This effect of NMDA was abolished when glands were coincubated with MK801 (a pharmacological blocker of the NMDA channel) or PD98059 (an inhibitor of the ERK-MAPK pathway). Glands obtained from animals with 2HPT showed no effect of NMDA in the in vitro release of PTH, together with a decrease in the expression of NMDAR1. In conclusion, NMDA receptor is present in PTG and is involved in the regulation of the PTH release. The mechanism by which NMDAR exerts its function is through the activation of the MAPK cascade. In uremic 2HPT animals the receptor expression is downregulated and the treatment with NMDA does not affect PTH secretion.

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Calcium balance in haemodialysis—do not lower the dialysate calcium concentration too much (con part)

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfp365 ◽

2009 ◽

Vol 24 (10) ◽

pp. 2990-2993 ◽

Cited By ~ 41

Author(s):

Tilman B. Drüeke ◽

Malik Touam

Keyword(s):

Calcium Concentration ◽

Calcium Balance ◽

Dialysate Calcium

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The Influence of Dialysate Calcium Concentration on the Pth Level in Children Undergoing Capd

Peritoneal Dialysis International ◽

10.1177/089686089601601s117 ◽

1996 ◽

Vol 16 (1_suppl) ◽

pp. 567-569 ◽

Cited By ~ 6

Author(s):

Maria Sieniawska ◽

Maria Roszkowska-Blaim ◽

Beata Wojciechowska

Keyword(s):

Mass Transfer ◽

Peritoneal Dialysis ◽

Parathyroid Hormone ◽

Dwell Time ◽

Calcium Concentration ◽

Vitamin D Metabolites ◽

Intact Parathyroid Hormone ◽

Gland Function ◽

Dialysate Calcium ◽

Pth Level

In 12 children aged four-and-a-half to 18 years (mean 11 ±4.2) undergoing continuous ambulatory peritoneal dialysis (CAPO), serum intact parathyroid hormone (iPTH), ionized calcium (iCa) levels, and calcium mass transfer (CaMT) were measured on three consecutive days: day 1, after a four-hour interval between dialyses; on day 2, after four hours dwell time with peritoneal dialysis (PD) Ca 3.5 mEq/L; and on day 3, after four hours dwell time with PD Ca 2.5 mEq/L. A significantly more negative CaMT was found when PD Ca 2.5 mEq/L was used, as compared with values obtained using PD Ca 3.5 mEq/L. Significantly lower parathyroid hormone (PTH) values were found after the interval between exchanges. We conclude that in order to properly evaluate parathyroid gland function and to decide whether or not to give vitamin D metabolites, a protocol for determining PTH should be standardized.

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