Journal Article

Differential effects of vitamin D receptor activators on aortic calcification and pulse wave velocity in uraemic rats

William Noonan, Kristin Koch, Masaki Nakane, Junli Ma, Doug Dixon, Antoinette Bolin and Glenn Reinhart

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 23, issue 12, pages 3824-3830
Published in print December 2008 | ISSN: 0931-0509
Published online July 2008 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfn375
Differential effects of vitamin D receptor activators on aortic calcification and pulse wave velocity in uraemic rats

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Background. Vascular calcification is associated with an increase in cardiovascular mortality in stage 5 chronic kidney disease. To determine if vitamin D receptor activators (VDRAs) have differential effects in the pathogenesis of aortic calcification, we assessed the effects of paricalcitol and doxercalciferol in vivo using 5/6 nephrectomized (NX) rats. To quantify the functional consequences of vascular calcification, pulse wave velocity (PWV), an aortic compliance index, was measured.

Methods. NX rats were fed a diet containing 0.9% phosphorous and 0.6% calcium 4 weeks prior to and throughout the study. On Day 0, rats received vehicle or VDRA (0.083, 0.167 and 0.333 μg/kg, i.p.) three times per week for 6 weeks. At Day 0 and Weeks 2 and 6, blood was drawn and PWV was measured by Doppler ultrasound.

Results. VDRAs (0.167 and 0.333 μg/kg) consistently lowered PTH at Weeks 2 and 6. All doses of paricalcitol increased serum calcium at Week 6 but not at Week 2, while the two higher doses of doxercalciferol increased serum calcium at both Weeks 2 and 6. Treatment with paricalcitol (0.333 μg/kg) increased serum phosphorus at Weeks 2 and 6; these changes were not different from those observed in 5/6 NX rats. All doses of doxercalciferol increased serum phosphorus at Week 6. Paricalcitol had no effect on Ca × P; however, the two highest doses of doxercalciferol increased Ca × P at Weeks 2 and 6 above that observed in the 5/6 NX vehicle-treated group. There were no differences in aortic calcium and phosphorus contents at the end of 6 weeks among SHAM-, 5/6 NX- and paricalcitol-treated rats. However, treatment with the two higher doses of doxercalciferol caused a significant elevation in aortic calcium and phosphorus contents. Measurements of PWV demonstrated differential effects of VDRAs on vascular compliance. Paricalcitol produced no effects on PWV, while the two highest doses of doxercalciferol increased PWV at Week 6.

Conclusions. In uraemic rats with established secondary hyperparathyroidism, we demonstrate differential effects of paricalcitol and doxercalciferol on aortic calcification and PWV, independent of serum Ca, P and Ca × P, suggesting different mechanisms of action between VDRAs.

Keywords: cardiovascular complications; chronic kidney disease; paricalcitol; pulse wave velocity; vascular calcification; vitamin D receptor activator

Journal Article.  3556 words.  Illustrated.

Subjects: Nephrology

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