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

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)
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PMID:Intestinal vitamin D-dependent calbindin-D9k and alkaline phosphatase in spontaneously hypertensive rats. 203 38

Human colon carcinoma (HT-29) cells were examined for their capacity to bind and respond to 1,25-dihydroxycholecalciferol [1,25-(OH)2D3]. These cells are known to differentiate and increase their population doubling time when galactose is substituted for glucose in their media. High-affinity and specific binding of 1,25-(OH)2[3H]D3 was observed in extracts of these cells grown in glucose. The binder sedimented in sucrose gradients and eluted from DEAE-cellulose columns in a manner indistinguishable from rabbit intestinal 1,25-(OH)2D3-receptor. Smaller amounts of this binder were seen in HT-29 cells grown in galactose. Both glucose-fed and galactose-fed cells exhibited a dose-dependent decrease in growth rate on exposure to 10(-12) to 10(-6) mol/L 1,25-(OH)2D3. Ultrastructural examination of galactose-fed and glucose + 1,25-(OH)2D3-treated cells showed enterocytic differentiation and features that were not distinguishable between these groups. Sucrase activity was higher in galactose-fed cells and did not change with 1,25-(OH)2D3 treatment. However, the lower sucrase activity in glucose-fed cells increased after exposure to 10(-8) mol/L 1,25-(OH)2D3. These results indicate receptor content and bioresponsivity to 1,25-(OH)2D3 in a human enterocytic cell line, suggesting that it will be a useful model for the study of the mechanisms of action of this sterol.
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PMID:Receptors for and bioresponses to 1,25-dihydroxyvitamin D in a human colon carcinoma cell line (HT-29). 255 92

The effect of vitamin D status on the topography of intestinal cell membranes was studied in isolated brush borders, as well as their purified membranes, by limited proteolysis. Addition of papain to brush borders isolated from vitamin D3-treated and deficient chicks resulted in a differential solubilization of leucine aminopeptidase, maltase, and sucrase activities (114, 195, and 79%, respectively, of appropriate control levels) but not alkaline phosphatase activity. In comparison, proteolysis of purified membranes exhibited vitamin D3- and 1,25-dihydroxycholecalciferol [1,25(OH)2D3]-dependent differences in release of all four marker hydrolases monitored. Calcium uptake studies revealed that preincubation with papain yielded vesicles with a calcium content that was 125% of corresponding native vesicles, in preparations from vitamin D3-treated, as well as deficient birds. Membrane vesicles prepared from 1,25(OH)2D3-treated chicks initially accumulated calcium to a greater extent than those from rachitic birds, but thereafter exhibited a decline in calcium content to basal levels. Preincubation with papain, however, abolished this loss of calcium. The combined results indicate that vitamin D mediates alterations in brush border protein topography and raise the possibility that this action of the seco-steroid might be involved in calcium absorption. However, if vitamin D-stimulated calcium transport across the brush border is dependent on a protein carrier, the molecular entity is not sensitive to inactivation by papain.
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PMID:Vitamin D-mediated alterations in the topography of intestinal brush border proteins: effect of papain on hydrolase release and calcium uptake. 684 6