1,25-Dihydroxyvitamin D3-mediated vesicular transport of calcium in intestine: time-course studies

Journal Article · Wed Jun 01 00:00:00 EDT 1988 · Endocrinology; (United States)

DOI:https://doi.org/10.1210/endo-122-6-2962· OSTI ID:6975083

Nemere, I; Norman, A W

Previous work has biochemically identified lysosomes containing calcium and calbindin-D28K (CaBP) in chick intestine that are sensitive to 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) status. In the present work, lysosomal accumulation of 45Ca was optimal after 30 min of absorption from in situ ligated duodenal loops. The areas under the curves, defined as lysosomal fractions in Percoll gradients, were calculated, and values after 10, 20, 30, and 40 min of transport were (+D/-D ratio) 0.90, 1.62, 1.88, and 1.78, respectively. Lysosomal CaBP also increased in parallel with the time of absorption and was not due to nonspecific adsorption. When lysosomal 45Ca was determined 2.5, 5, 10, 15, and 43 h after administration of 1.3 nmol 1,25-(OH)2D3 or vehicle, the area ratios were 1.02, 1.47, 3.10, 1.88, and 1.29, respectively. Analyses of serum 45Ca in the same birds yielded a closely parallel time course with 1,25-(OH)2D3-dependent intestinal calcium absorption; values were 108 +/- 12% (+/- SE), 164 +/- 29%, 300 +/- 35%, 340 +/- 39%, and 169 +/- 8% of vitamin D-deficient control values at 2.5, 5, 10, 15, and 43 h, respectively. Immunoreactive CaBP in lysosomal fractions did not change significantly between 5-43 h after administration of seco-steroid. A similar series of experiments was conducted with microsomal membranes containing putative endocytic vesicles, which are believed to deliver calcium to the lysosomes. The brush border origin of the vesicles was supported by the internalization of anti-CaBP immunoglobulin G after 3 min of absorption. Accumulation of 45Ca by endocytic vesicles was subsequently found to be maximal after 20 min of absorption (+D/-D = 1.48), declining again at 30 min (+D/-D = 1.16), while CaBP levels in the same fractions remained unchanged between 0-30 min of absorption.

• Research Organization: Univ. of California, Riverside (USA)
• OSTI ID: 6975083
• Journal Information: Endocrinology; (United States), Vol. 122:6
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CALCIUM
INTESTINAL ABSORPTION
MEMBRANE TRANSPORT
VITAMIN D
INTESTINES
NUTRITIONAL DEFICIENCY
BIOCHEMICAL REACTION KINETICS
CALCIUM 45
CELL MEMBRANES
CHICKENS
ENDOPLASMIC RETICULUM
LYSOSOMES
MICROSOMES
TRACER TECHNIQUES
ABSORPTION
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIRDS
BODY
CALCIUM ISOTOPES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
ELEMENTS
EVEN-ODD NUCLEI
FOWL
GASTROINTESTINAL TRACT
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MEMBRANES
METALS
NUCLEI
ORGANOIDS
ORGANS
RADIOISOTOPES
REACTION KINETICS
UPTAKE
VERTEBRATES
VITAMINS
550201* - Biochemistry- Tracer Techniques