Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Insulin affects the expression of brush border enzymes by villus cells in vitro and in vivo. Physiological (lactation) and surgical (jejunoileal bypass) models of hyper- and hypoplasia were established so that insulin receptor characteristics could be related to villus histology, expression of sucrase and alkaline phosphatase, and plasma insulin concentrations. In lactating rats, villus height increased up to 55% (p less than 0.005), and fasting plasma insulin increased 71% (p = 0.005), compared with controls. Insulin binding to villus cell membranes, and sucrase and alkaline phosphatase activities were, however, unchanged. In ileum of bypass operated rats, villus height increased 134% (p less than 0.005) while insulin binding fell 68% (p = 0.025). Scatchard analysis revealed that this was largely because of reduction in binding by high affinity receptors. Sucrase and alkaline phosphatase specific activities fell 57% (p = 0.03) and 49% (p = 0.02) respectively, suggesting that ileal villus cells were hypomature. The slightly hypoplastic tissue of selfemptying loops showed normal insulin binding compared to jejunum of sham operated controls. Bypass and sham operated rats had similar fasting plasma insulin concentrations. Reduced insulin binding in markedly hyperplastic gut of bypass operated rats might reflect hypomaturity of villus cells. The reduction in insulin binding, however, might significantly modulate the effect of insulin on small intestinal mucosa and account for the fall in enzyme activity which occurs despite villus hyperplasia.
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PMID:Effects of intestinal adaptation on insulin binding to villus cell membranes. 331 13

Adaptive growth and precocious expression of sucrase activity occur in the small intestine of artificially reared (AR) rat pups fed a hormone-free diet. The physiological mechanisms underlying adaptive intestinal growth were studied. Day 12 rat pups that received jejunal isografts subcutaneously on day 0 were subjected to artificial feeding and were killed on day 16. Crypt cellularity and DNA labeling index in isografts from AR, but not from mother-fed, rats increased significantly to levels found in in situ host jejunum of AR rats, indicating that humoral regulatory mechanisms are responsible for intestinal cell proliferation in AR pups. Radioimmunoassays of serum corticosterone, thyroxine, insulin, and gastrin and of gastric gastrin contents revealed that only serum corticosterone concentrations were significantly elevated, suggesting that corticosterone plays a critical role for intestinal growth. To examine this possibility directly, day 12 rats were adrenalectomized (ADX) and AR by continuous infusion of diets containing 0, 10, or 50 micrograms/ml corticosterone. Serum corticosterone concentrations paralleled the infused doses of corticosterone. Jejunal DNA labeling index increased in all ADX AR rats at day 13 in a dose-dependent manner. Increased jejunal DNA labeling index was maintained on day 14 in intact AR rats and ADX AR rats fed 10 micrograms/ml corticosterone but not in ADX AR rats receiving 0 or 50 micrograms/ml. We conclude that endogenous corticosterone is one of the systemic factors responsible for the adaptive increase in intestinal growth of AR rats.
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PMID:Hormonal regulation of adaptive intestinal growth in artificially reared rat pups. 332 40

The effects of epidermal growth factor transforming growth factor beta (TGF beta) and other growth factors on the proliferation and differentiation of a cell line derived from rat intestinal crypt epithelium (IEC-6) were defined. Incorporation of [3H]-thymidine was stimulated 1.4-2.4 fold by insulin, insulin like growth factor (IGF), platelet derived growth factor (PDGF), epidermal growth factor (EGF) and 2% fetal calf serum (FCS) respectively. Additive stimulation was observed when FCS was supplemented by insulin,IGF-I or PDGF but not EGF. Incorporation of [3H]-thymidine by IEC-6 was strongly inhibited by TGF beta with greater than 80% inhibition of incorporation at concentration approximately equal to 2.0 pM. IEC-6 cells bound 4.1 +/- 0.15 X 10(4) molecules TGF beta/cell and appeared to have only a single class of high affinity receptors (Kd approximately equal to 0.5 pM). TGF beta inhibition was unaffected by the presence of insulin or IGF-I suggesting it inhibits proliferation at a step subsequent to that at which these growth factors stimulate [3H]-thymidine incorporation. TGF beta also reduced the stimulation induced by FCS by 65%. In contrast EGF reduced TGF beta inhibition by 60%. IEC-6 cells demonstrated the appearance of sucrase activity after greater than 18 hours treatment with TGF beta. These findings suggest that TGF beta may inhibit proliferative activity and promote the development of differentiated function in intestinal epithelial cells.
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PMID:Effects of growth factors on an intestinal epithelial cell line: transforming growth factor beta inhibits proliferation and stimulates differentiation. 354 18

Intestinal adaptation has been studied in rats with pancreatic atrophy induced by feeding a copper-deficient diet and penicillamine and in rats with carbohydrate maldigestion induced by feeding of an alpha-glucosidase inhibitor (acarbose). Pancreatic atrophy led to a significant increase of weight, protein, and DNA content as well as specific activities and total amounts of the enzymes sucrase and maltase in the distal but not in the proximal part of the small intestine. Plasma levels of CCK and GIP were significantly higher in rats with pancreatic atrophy, whereas plasma levels of gastrin and insulin were lower. Tissue concentrations of gastrin in the antrum and GIP in duodenum and jejunum were unchanged. Duodenal CCK and jejunal substance P, somatostatin, and VIP and ileal substance P and somatostatin were significantly decreased in rats with acinar atrophy. Glucosidase inhibition by acarbose feeding led to weight increase of the small intestine and cecum. This was more marked when acarbose was fed together with a fiber-free diet. Under these conditions the protein and DNA content also increased significantly in both gut segments and maltase and sucrase content predominantly in the distal part. Insulin plasma concentration decreased significantly in the acarbose-fed groups, whereas GIP, gastrin, and CCK plasma concentrations remained unchanged. After fiber-rich diet tissue concentrations of gastrin in the antrum and insulin in the pancreas were significantly higher and GIP concentrations in the duodenum and jejunum significantly lower than after fiber-free diet. Acarbose increased the pancreatic insulin concentration only in the fiber-free group and did not influence gastrin and GIP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adaptation of the small intestine to induced maldigestion in rats. Experimental pancreatic atrophy and acarbose feeding. 389 54

Diabetes was induced in rats by administration of streptozotocin. After 90-120 days, one group of chronic diabetic animals was treated with insulin for chronic diabetic animals was treated with insulin for 10 days. The lipid fluidity and composition of microvillus membranes prepared from ileal enterocytes of control, diabetic, and insulin-treated diabetic animals were determined. Lipid fluidity, as assessed by steady-state fluorescence polarization techniques using the probes 1,6-diphenyl-1,3,5-hexatriene, DL-2-(9-anthroyl)stearic acid and DL-12-(9-anthroyl)stearic acid, was decreased in membranes of diabetic animals compared to membranes of control and insulin-treated diabetic membranes. The differences in fluidity resulted from an increased cholesterol content and cholesterol/phospholipid molar ratio in membranes of diabetic animals. The activities of sucrase and alkaline phosphatase were also found to be higher in membranes of diabetic animals. Insulin treatment, however, failed to significantly influence the enzymatic activities of these membranes. These studies, therefore, demonstrate that alterations in the lipid fluidity, lipid composition, and certain enzymatic activities exist in microvillus membranes of enterocytes prepared from chronic streptozotocin-induced diabetic rats. Administration of insulin for 10 days to these animals restored membrane fluidity and lipid composition but not enzymatic activities to control membrane levels.
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PMID:Correction of abnormal lipid fluidity and composition of rat ileal microvillus membranes in chronic streptozotocin-induced diabetes by insulin therapy. 390 76

The effects of experimental diabetes, hypertonic glucose infusion, and subsequent insulin administration on the sucrase activity of the small intestine were studied using intestinal segments completely excluded from luminal continuity by construction of Thiry-Vella fistulas in rats. Eight weeks after subtotal pancreatectomy, the rats contracted insulin-deficient diabetes mellitus, and sucrase activity was enhanced in both the Thiry-Vella loop and in the proximal jejunum in continuity. Subcutaneous injections of insulin during the last 4 weeks maintained the enzyme activity in the control range in both segments. There was a positive correlation between sucrase activity and blood glucose level in the pancreatectomized rats. Hyperglycemia in normal rats induced by intravenous infusion of 30% glucose solution over 48 hours enhanced the sucrase activity in the jejunum. Furthermore, insulin administration with a glucose solution inhibited the enhancement of enzyme activity. These findings suggest that hyperglycemia itself might play an important role in the diabetic increment of sucrase activity.
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PMID:Hyperglycemia induces intestinal sucrase activity in subtotally pancreatectomized rats. 401 94

Explants of suckling mouse jejunum have been maintained in serum-free organ culture with or without insulin added to the medium in order to determine the possible direct effect of this hormone on the hydrolytic functions of the brush border and on the proliferation of the crypt cells. The addition of insulin induced the precocious appearance of sucrase activity and increased trehalase, glucoamylase and lactase activities. Alkaline phosphatase activity remained unaffected in the tissue as well as in the medium. An increased DNA content and 3H-thymidine incorporation into DNA were already recorded after 24 h of culture. The mitotic index was significantly increased after 24 h and remained elevated when the culture was extended to 48 h. These results show that insulin directly influences the enzymatic maturation and the proliferation of intestinal epithelial cells of suckling mouse.
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PMID:Insulin influences the maturation and proliferation of suckling mouse intestinal mucosa in serum-free organ culture. 639 67

Fasting reduced small intestinal length. It also decreased mucosal weight, DNA and protein content, and concentrations of enterokinase, maltase, and sucrase in both duodenal and jejunal segments. In contrast, the concentrations of lactase and leucine aminopeptidase were not affected. Concomitantly, serum insulin levels dropped to one-fifth of the control levels while serum glucose concentrations showed a lesser degree of reduction. Glucose supplementation alone raised the serum insulin level, prevented the decrease in DNA content, and showed a protective effect on mucosal protein, mucosal weight, mucosal thickness, and villus height. Glucose also protected the sucrase and maltase concentrations; more significantly for maltase in the jejunal segment. Insulin alone, although it increased the serum insulin level to that found with glucose supplementation alone, had no protective effect on the loss in protein, DNA, and most enzymes except for maltase concentration in the jejunal segment. Addition of insulin to glucose did not modify the glucose effect on the contents of DNA, protein, and concentrations of sucrase and maltase. These results suggest that the glucose effect on the mucosa is not mediated by insulin. In addition, the retention of both maltase and sucrase activities through only glucose supplementation suggests the loss of maltase and sucrase in fasting is due to nutrient rather than specific substrate restriction.
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PMID:Effect of glucose and insulin on small intestinal brush border enzymes in fasted rats. 640 48

Jejunal mucosa of 6 d-old rats were cultured for 24 and 48 h in the presence of thyroxine, insulin, pentagastrin, glucagon, epidermal growth factor (EGF) or dibutyryl-A-3:5-MP cyclic with or without dexamethasone (DX). The enzymes were assayed on the purified brush borders. The various agents added alone to the basic culture medium had no effect with the exception of DX on the levels of enzyme activities. Dexamethasone alone induced sucrase, stimulated maltase, and protected other brush border enzyme activities (aminopeptidase, lactase, and alkaline phosphatase). When added to DX-supplemented medium, only the following factors modified the levels of enzymatic activities observed with DX alone. Insulin (10(-6) M) increased maltase, alkaline phosphatase, and lactase activity to a greater extent than DX at 24 h culture, the effect being maintained at 48 h on alkaline phosphatase only. At 48 h culture, both EGF (10(-8) M) and dbcAMP (10(-3) M) decreased DX-induced sucrase activity. The latter agent also depressed DX-stimulated aminopeptidase activity.
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PMID:Organ culture of suckling rat intestine: comparative study of various hormones on brush border enzymes. 674 50

The development of alkaline phosphatase, maltase, and sucrase activities in the duodenum of the chick embryo was followed in organ culture in chemically defined medium; 14-day duodenum was used in most experiments, with comparisons being made with 18-day tissue. As has been previously shown for the other enzymes, sucrase activity also rises at an accelerated rate in vitro. Since chick sucrase has maltase activity, its increase appears to account for the spontaneous rise of maltase activity; the form of maltase devoid of sucrase activity seems not to be accelerated. Sucrase, sucrase-free maltase, and alkaline phosphatase are all elevated by the addition of insulin to the medium. Intestinal sucrase is well known to be responsive to hydrocortisone, but it has now been found to be unresponsive to thyroxine, except that its dissociation from the brush border is increased at hormone concentrations above 1 nM. Insulin and thyroxine act synergistically on alkaline phosphatase, but the addition of hydrocortisone diminishes the effect of the other two. With sucrase, insulin and hydrocortisone have a synergistic effect which is intensified by addition of thyroxine. The previously demonstrated influence of hydrocortisone on maltase is accounted for by the maltase activity of sucrase. In combination, however, hydrocortisone and thyroxine elevated maltase much more strongly than sucrase, and the highest maltase levels were attained when all three hormones were present.
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PMID:Chick embryo intestine in culture: influence of insulin and other hormones on sucrase, maltase, and alkaline phosphatase. 676 10


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