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- Title
Effects of fasting, feeding, and bisphosphonate administration on serum calcitriol levels in phosphate-deprived rats.
- Authors
Felsenfeld, Arnold J.; Jara, Aquiles; Avedian, Gabrielle; Kleeman, Charles R.
- Abstract
Effects of fasting, feeding, and bisphosphonate administration on serum calcitriol levels in phosphate-deprived rats. Background. In a recent study, we showed in phosphate-deprived rats that morning feeding decreased serum phosphate and increased serum calcium values as compared with similar rats fasted overnight, and high doses of bisphosphonates did not reduce the magnitude of hypercalcemia. In the present study, we evaluated in phosphate-deprived rats whether serum calcitriol values were: (1) affected by the differences in serum phosphate induced by morning feeding and overnight fasting, (2) correlated with changes in serum phosphate levels, and (3) influenced by bisphosphonate administration. Methods. Four groups of rats were studied: (1) low-phosphate diet (LPD; P < 0.05%), (2) LPD + the bisphosphonate pamidronate (APD), (3) normal diet (ND; P 0.6%), and (4) ND + APD. Both diets contained 0.6% calcium. In rats receiving APD, high doses (0.8 mg/kg) were given subcutaneously four times during the study. On day 11, rats were sacrificed after an overnight fast or two to four hours after morning feeding. Results. In the fed phosphate-deprived rats (LPD and LPD + APD), serum phosphate levels were less (P < 0.05) and serum calcium levels were greater (P < 0.05) than in similar rats fasted overnight. In rats on the ND (ND and ND + APD), no differences were observed between fed and fasted rats. In phosphate-deprived rats, serum calcitriol levels were greater (LPD, P < 0.05) or tended to be greater (LPD + APD, P = 0.10) in the fed than in the fasted groups. In APD-treated rats, serum calcitriol values were greater than in rats not given APD whether rats were (1) fed or fasted, or (2) on an LPD or ND. An inverse correlation was present between serum phosphate and serum calcitriol (r = -0.58, P = 0.001). In a stepwise regression model in which serum calcitriol was the dependent variable and independent variables were APD administration and serum calcium, phosphate, and...
- Subjects
FASTING; PHOSPHATES; HYPOPHYSECTOMY; PHYSIOLOGY
- Publication
Kidney International, 2000, Vol 58, Issue 3, p1016
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1046/j.1523-1755.2000.00259.x