Separate effects of 1,25-dihydroxyvitamin D and calcium on renal calbindin-D28k and intestinal calbindin-D9k.
The effects of normal, low and high plasma concentrations of 1,25-(OH)2vitamin D (1,25-(OH)2D) combined with normal, low and high concentrations of plasma calcium on renal calbindin-D28k and intestinal calbindin-D9k were examined in rats. We found that the expression of renal calbindin-D28k was significantly (P<0.05) increased by high levels of 1,25-(OH)2D, but was not affected by a 50% reduction in 1,25-(OH)2D. In contrast the intestinal calbindin-D9k responded significantly (P<0.005) to both high and low 1,25-(OH)2D levels. The effect of 1,25-(OH)2D on intestinal calbindin-D9k was modulated by plasma calcium concentrations. Increased plasma calcium levels did not affect the renal calbindin-D28k concentrations, but suppressed intestinal calbindin-D9k (P<0.05). The effect of calcium was not mediated by calciotropic hormones. This suggests the existence of a calcium-sensing mechanism in the proximal duodenum. It is concluded that intestinal calbindin-D9k is more sensitive than renal calbindin-D28k to changes in 1,25-(OH)2D and that intestinal calbindin-D9k in contrast to renal calbindin-D28k is sensitive to changes in plasma calcium concentrations.
Hemmingsen
Claus
C
Critical Care Clinic, Copenhagen, Denmark. clhe@dadlnet.dk
Staun
Michael
M
Nielsen
Palle K
PK
Olgaard
Klaus
K
D000818:Animals; D064092:Calbindin 1; D064026:Calbindins; D002118:Calcium / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004032:Diet; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology*
C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D010281:Parathyroid Hormone; D064030:S100 Calcium Binding Protein G; C576508:S100g protein, rat; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D002118:Calcium