Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suckling rats. The mechanism of this effect is unknown, as are the roles of vitamin D-dependent and independent pathways. The present studies were undertaken to investigate the ability of EGF to accelerate the postnatal induction of the vitamin D-dependent intestinal calcium-binding protein, calbindin-D9k. Subcutaneous administration of EGF increased duodenal calbindin-D9k in suckling rats by more than 100% (P less than 0.001). The effect of EGF was not seen in older weaned animals or when EGF was given to suckling rats by gavage. Administration of EGF simulated the changes of normal development. 1) It increased calbindin-D9k, and the effect was greater in proximal than distal duodenum. 2) EGF increased alkaline phosphatase activity to the same extent in proximal and distal duodenum. 3) EGF increased sucrase more markedly in distal than in proximal epithelium. Maximal and half-maximal effects of EGF on each of these proteins were observed at twice daily doses of 0.1 and 0.04 microgram/g BW, respectively. 4) EGF at the maximally effective dose produced a small (30%) but statistically significant (P less than 0.005) increase in serum 1,25-dihydroxyvitamin D. 5) Most importantly, EGF treatment resulted in a 2-fold increase in intestinal 1,25-dihydroxyvitamin D receptors (VDR) in the proximal segments of the small intestine (P less than 0.001). EGF effects on calbindin-D9k and VDR were specific for the intestine, as EGF did not change kidney calbindin-D9k or kidney VDR. Thus, EGF was able to prematurely initiate a complex series of molecular changes that occur during normal development. The mechanism of EGF's action to stimulate calcium absorption appears to involve a maturation effect on the vitamin D-dependent pathway.
 ...
PMID:Epidermal growth factor increases intestinal calbindin-D9k and 1,25-dihydroxyvitamin D receptors in neonatal rats. 254 9

To determine which region of the intestinal villus was primarily responsible for calcium uptake and whether cells from the different regions of the villus differed in their response to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], we studied cells eluted from the duodenal villus in a sequential fashion at various times after vitamin D-deficient chicks had received 1,25-(OH)2D3. The elution scheme employed removes cells from the villus tip first and cells from the villus base last, as was documented by the distribution of alkaline phosphatase activity, sucrase activity, and cytosolic calcium-binding protein (CaBP) in the eluted fractions. Brush border membrane vesicles (BBMV) were prepared from different fractions of the villus. Calcium uptake was greatest in BBMV from cells eluted from the villus tip and least in those from the villus base. The distribution of calcium uptake and alkaline phosphatase activity in the same BBMV were parallel. After 1,25-(OH)2D3 treatment, cytosolic CaBP was observed in the cells from the villus base by 4 h and in all fractions by 8 h; at all times (from 4-24 h), cells from the villus base contained more cytosolic CaBP than did cells from the villus tip. Alkaline phosphatase activity in BBMV was stimulated in all fractions by 4 h; at all times, alkaline phosphatase activity was greatest in BBMV from cells of the villus tip. In contrast, calcium uptake by BBMV was stimulated 2 h after 1,25-(OH)2D3 administration only in cells from the villus tip and was not stimulated even by 24 h in cells from the villus base. These results indicate that the cellular response to 1,25-(OH)2D3 depends on the location of the cell on the villus and that 1,25-(OH)2D3-stimulated calcium flux across the brush border can be dissociated from 1,25-(OH)2D3-stimulated alkaline phosphatase activity and CaBP production.
 ...
PMID:Differential response of duodenal epithelial cells to 1,25-dihydroxyvitamin D3 according to position on the villus: a comparison of calcium uptake, calcium-binding protein, and alkaline phosphatase activity. 654 95