25-Hydroxycholecalciferol as an antagonist of adverse corticosteroid effects on phosphate and calcium metabolism in man

Age-dependent regulation of rat intestinal type IIb sodium-phosphate cotransporter by 1,25-(OH)(2) vitamin D(3)

The current studies were designed to characterize type IIb sodium-inorganic phosphate (P(i)) cotransporter (NaP(i)-IIb) expression and to assess the effect of 1,25-(OH)(2) vitamin D(3) on NaP(i)-IIb gene expression during rat ontogeny. Sodium-dependent P(i) absorption by intestinal brush-border membrane vesicles (BBMVs) decreased with age, and NaP(i)-IIb gene expression also decreased proportionally with age. 1,25-(OH)(2) vitamin D(3) treatment increased intestinal BBMV P(i) absorption by approximately 2.5-fold in suckling rats and by approximately 2.1-fold in adult rats. 1,25-(OH)(2) vitamin D(3) treatment also increased NaP(i)-IIb mRNA abundance by approximately 2-fold in 14-day-old rats but had no effect on mRNA expression in adults. Furthermore, in rat intestinal epithelial (RIE) cells, 1,25-(OH)(2) vitamin D(3) increased NaP(i)-IIb mRNA abundance, an effect that was abolished by actinomycin D. Additionally, human NaP(i)-IIb gene promoter activity in transiently transfected RIE cells showed approximately 1.6-fold increase after 1,25-(OH)(2) vitamin D(3) treatment. In conclusion, we demonstrate that the age-related decrease in intestinal sodium-dependent P(i) absorption correlates with decreased NaP(i)-IIb mRNA expression. Our data also suggest that the effect of 1,25-(OH)(2) vitamin D(3) on NaP(i)-IIb expression is at least partially mediated by gene transcription in suckling rats.

Serum levels of calcitonin in Cushing's syndrome

Serum levels of calcitonin (CT) were studied in 21 patients with Cushing's syndrome (CS), 18 females and 3 males aging from 16 to 59 years, and in 70 age and sex matched normal subjects. Patients with CS showed CT values significantly lower than those found in controls (9.9 +/- 5.0 pg/ml vs. 15.9 +/- 6.3 pg/ml, mean +/- SD; p less than 0.01), while no difference was observed in total serum calcium and phosphate and calcium corrected for albumin. No correlation between CT and serum calcium and phosphate, serum cortisol and urinary free cortisol was found. It is possible that low CT levels are involved in the pathogenesis of bone loss observed in CS.