Intestinal vitamin D-dependent calbindin-D9k and alkaline phosphatase in spontaneously hypertensive rats.
Intestinal Ca2+ malabsorption has been described in spontaneously hypertensive rats (SHRs), but the molecular basis for this defect is unknown. In this study, we measured intestinal alkaline phosphatase and vitamin D-dependent Ca(2+)-binding protein (calbindin-D9k), two proteins implicated in the active pathway of intestinal Ca2+ absorption. Both proteins were measured in the small intestines of SHRs and their normotensive controls, Wistar-Kyoto rats, before, during, and after development of hypertension (4, 9, 14, 18, and 28 wk of age). At all ages, alkaline phosphatase activity in duodenum (0-6 cm) was decreased by 30-57% (P less than 0.001) and by 47-75% in the 2nd intestinal segment (6-12 cm) (P less than 0.001-0.05). Calbindin-D9k was decreased similarly. The decreases of calbindin were statistically significant (P less than 0.001-0.05) in the duodena at 4, 14, 18, and 28 wk (9-30% decreases) and in the 2nd segment at 4, 14, and 18 wk (38-69% decreases; P less than 0.001-0.005). Decreased calbindin in SHRs was documented in animals from two suppliers. The deficiencies of calbindin-D9k and alkaline phosphatase could not be attributed to malnutrition or to a generalized brush-border defect as indicated by body weights and the intestinal marker enzyme sucrase. Although calbindin-D9k was decreased in young SHRs, the serum 1,25-dihydroxycholecalciferol [1,25(OH)2D3] was increased by 59 and 129% in 4- and 9-wk-old SHRs (P less than 0.001), respectively; by contrast, serum 1,25(OH)2D3 was unchanged or decreased in older SHRs.(ABSTRACT TRUNCATED AT 250 WORDS)
Cloney
D L
DL
Department of Pathology, University of Virginia School of Medicine, Charlottesville 22908.
Gray
R W
RW
Bruns
M E
ME
Burnett
S H
SH
Smith
M L
ML
Felder
R A
RA
Bruns
D E
DE
D000375:Aging; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001794:Blood Pressure; D001835:Body Weight; D064026:Calbindins; D006973:Hypertension / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013045:Species Specificity
D064026:Calbindins; D064030:S100 Calcium Binding Protein G; C576508:S100g protein, rat; D000469:Alkaline Phosphatase