Intestinal phospholipase A and triglyceride lipase: localization and effect of fasting

We assessed intestinal structure, mucosal epithelial kinetics, and disaccharidase activities after fasting. Rats fasted for up to 120 hours were compared with control rats fed ad libitum. All rats had free access to water and all were prevented from ingesting their own stools. Body weight, small intestinal weight and mucosal protein, and maltase and sucrase activity of the total small intestine decreased in fasted rats. Lactase activity did not decrease. Specific activity of lactase actually increased in the jejunum. Assessed after a 96-hour fast, jejunal villi were shortened with less epithelial cells along their length and the rate of migration of those cells along the villi was diminished in the fasted rats compared with control rats. We attribute the decreased total intestinal sucrase and maltase activities to a loss of total epithelial cell mass in the small bowel. An abnormality in the cells of the progenitor zone of the crypts is suggested by the decreased migration rate of mucosal epithelial cells in fasting rats. These factors do not explain our observations completely since lactase activity did not diminish. We postulate that the activity of the "acid" β-galactosidase located in the cytoplasm or lysosomes of the epithelial cells was stimulated by fasting. Our observations are relevant to clinical pediatrics. Undernutrition and fasting my be associated with many childhood diseases and with treatment of disease. In assessing clinical data and advising treatment, the pediatrician should be aware of the potentially harmful effects of starvation on intestinal structure and function.

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Neurotensin stimulates [3H]oleic acid translocation across rat small intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1986.251.6.g823 ◽

1986 ◽

Vol 251 (6) ◽

pp. G823-G829 ◽

Cited By ~ 7

Author(s):

M. J. Armstrong ◽

M. C. Parker ◽

C. F. Ferris ◽

S. E. Leeman

Keyword(s):

Small Intestine ◽

Oleic Acid ◽

Mesenteric Artery ◽

Specific Activity ◽

Femoral Vein ◽

Lymph Flow ◽

Entire Length ◽

Intestinal Lumen ◽

Rat Small Intestine ◽

Series Of Experiments

The effect of neurotensin (NT) on the translocation of intraluminally administered lipid across the duodenum as well as across the entire length of the small intestine was studied in the rat. In the first series of experiments, the appearance in the lymph of [3H]oleic acid instilled as a bolus into a segment of the duodenum was followed for 3 h. Infusion of NT (0.6 pmol X kg-1 X min-1) via the superior mesenteric artery resulted in a significant increase in the appearance of label in the lymph when compared with saline infusion (17.3 +/- 3.1 vs. 8.6 +/- 1.4%, P less than 0.01, respectively). In the second series of experiments, lipid was infused into the entire length of the small intestine over 4 h, and the accumulation of label in the lymph was measured. The infusion of NT (1.0 pmol X kg-1 X min-1) into the femoral vein also significantly increased the appearance of label when compared with animals infused with saline (49.0 +/- 2.0 vs. 34.2 +/- 5.2%, P less than 0.05, respectively). In this study, the specific activity of the triglyceride recovered in the lymph was higher in the rats given NT than in the controls (P less than 0.05). No significant changes in lymph flow were observed as a consequence of NT infusion. These results indicate that NT infusion into the circulation increases the translocation of oleic acid from the intestinal lumen into the lymph of rats.

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The effect of starvation on the control of phosphofructokinase activity in the epithelial cells of the rat small intestine

Biochemical Journal ◽

10.1042/bj2100129 ◽

1983 ◽

Vol 210 (1) ◽

pp. 129-135 ◽

Cited By ~ 21

Author(s):

A Jamal ◽

G L Kellett

Keyword(s):

Small Intestine ◽

Epithelial Cells ◽

Terminal Ileum ◽

Specific Activity ◽

Utilization Rate ◽

Proximal Jejunum ◽

Rat Small Intestine ◽

Humoral Factors ◽

Specific Activities ◽

Regulatory Properties

1. The effect of depriving rats of food for 48 h on the specific activity of phosphofructokinase in the epithelial cells of the small intestine and on the regulatory properties of the enzyme displayed in crude (particle-free) mucosal extracts was studied. 2. The specific activity of phosphofructokinase, measured under optimal conditions at pH8, in the mucosa of fed rats showed a negative aboral gradient along the intestine, decreasing from 15.2 +/- 1.2 units (mumol/min)/g wet wt. in the proximal jejunum to 4.6 +/- 1.2 units/g wet wt. in the terminal ileum. 3. After starvation, the gradient was diminished, but not abolished; the diminution in gradient was due almost exclusively to a decrease in the specific activity of phosphofructokinase in the proximal jejunum by about 30%, there being no change in the terminal ileum. 4. In fed rats, the susceptibility of phosphofructokinase to inhibition by ATP, when assayed in crude mucosal extracts under suboptimal conditions, was independent of length along the small intestine; the ratio of the activity observed at pH 7.0 in the presence of 0.5 mM-fructose 6-phosphate and 2.5 mM-ATP to the optimal activity at pH 8, v0.5/V, was 0.36 +/- 0.05 in the proximal jejunum and 0.42 +/- 0.07 in the terminal ileum. 5. After starvation, the susceptibility of phosphofructokinase to inhibition by ATP was increased and was again found to be independent of length along the small intestine: after starvation, v0.5/V was 0.19 +/- 0.04 and 0.20 +/- 0.07 for the proximal jejunum and the terminal ileum respectively. 6. Re-feeding of previously starved rats on a high-carbohydrate diet overnight for 16 h restored both the specific activities of phosphofructokinase and its susceptibility to inhibition by ATP to normal values for fed rats. 7. The data support the idea that the specific activities and the regulatory properties of phosphofructokinase in the epithelial cells of rat small intestine are mediated by distinct humoral factors. 8. The changes in glucose utilization rate of the jejunum when rats are starved can in principle be accounted for by a combination of changes in the specific activity and in the regulatory properties of mucosal phosphofructokinase.

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The effect of pectin on the structure and function of the rat small intestine

British Journal Of Nutrition ◽

10.1079/bjn19790125 ◽

1979 ◽

Vol 42 (3) ◽

pp. 357-365 ◽

Cited By ~ 62

Author(s):

R. C. Brown ◽

J. Kelleher ◽

M. S. Losowsky

Keyword(s):

Small Intestine ◽

Small Bowel ◽

Specific Activity ◽

Basal Diet ◽

Muscle Layer ◽

Glucose Absorption ◽

Structure And Function ◽

Rat Small Intestine ◽

And Function

1. The effect of pectin on the structure and function of the rat small intestine was compared with that of a standard pellet diet and of a fibre-free basal diet.2. The length and wet weight of the small bowel was significantly greater inpect in-fed rats than in either pellet- or basal-diet-fed rats.3. Histological measurements of longitudinal sections from the small bowel showed a significantly greater crypt depth and muscle layer thickness in the mid-jejunum and ileum of the pectin fed rats. Villous height showed less variation.4. The specific activity of alkaline phosphatase (EC 3.1.3.1)and leucyl-P-naphthylamidase (EC 3.4.11.1) in mucosal scrapings was significantly lower in the upper jejunum of pectin-fed rats compared with either of the other dietary groups. The differences were not so marked in mid-jejunum or ileum.5. Glucose absorption measured in vivo from jejunal and ileal loops was similar in all three dietary groups.6. With two minor exceptions there were no significant differences in any of these measurements between the pellet- and basal-diet-fed rats.7. These findings could be explained by increased epithelial cell turnover caused by pectin. The possible mechanisms of this are discussed.8. The effect of pectin on the human small bowel requires study before it can be widely prescribed in man.

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STUDIES ON THE DISTRIBUTION AND KINETICS OF THE ALKALINE PHOSPHATASE OF RAT SMALL INTESTINE

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y59-076 ◽

1959 ◽

Vol 37 (1) ◽

pp. 699-709 ◽

Cited By ~ 4

Author(s):

Eugenie Triantaphyllopoulos ◽

Jules Tuba

Keyword(s):

Alkaline Phosphatase ◽

Small Intestine ◽

Specific Activity ◽

Supernatant Fraction ◽

Magnesium Ion ◽

Rat Small Intestine ◽

Albino Rat ◽

Michaelis Constants ◽

Intestinal Enzyme ◽

Kinetics Of

Alkaline phosphatase activity was demonstrated throughout the entire length of the small intestine of the albino rat and the relative amounts present seemed to decrease exponentially from the pylorus to the ileocolic valve. All subcellular fractions of intestinal homogenates were found to hydrolyze sodium β-glycero-phosphate. The distribution of activity of the enzyme was as follows: "microsomes", about 76%; nuclei, 10%; mitochondria, 8%; and in the nongranular, supernatant fraction, 9%. The specific activity for these fractions was: 52, 3, 10, and 3, respectively. The effects of the time of incubation, pH of the hydrolytic mixture, and the concentration of the enzyme were similar in all fractions. For the enzyme in the various fractions slight differences were observed in the values of the Michaelis constants, and in the degree of activation by magnesium ion. These variations may be explained on the basis of differences in the accessibility of substrate and magnesium ion to the enzymes in the various fractions. The finding that the "microsomes" contained the highest levels of alkaline phosphatase suggests that this intestinal enzyme is produced almost entirely by these submicroscopic particles.

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The isolation and characterization of phosphofructokinase from the epithelial cells of rat small intestine

Biochemical Journal ◽

10.1042/bj2110373 ◽

1983 ◽

Vol 211 (2) ◽

pp. 373-379 ◽

Cited By ~ 13

Author(s):

S M Khoja ◽

N L Beach ◽

G L Kellett

Keyword(s):

Small Intestine ◽

Specific Activity ◽

Proteinase Inhibitors ◽

Deae Cellulose ◽

Native Enzyme ◽

Rat Small Intestine ◽

Cellulose Acetate Electrophoresis ◽

Isolation And Characterization ◽

Main Component ◽

Proteolytic Product

1. Only a single phosphofructokinase isoenzyme is present in the mucosa of rat small intestine. 2. Mucosal phosphofructokinase was purified to yield a homogeneous preparation of specific activity 175 units/mg of protein. 3. The native enzyme is a tetramer, with monomer Mr 84 500 +/- 5000. 4. The native enzyme may be degraded by the action of endogenous proteinases to give two products with the same specific activity as the native enzyme: degradation occurs in the order native enzyme leads to proteolytic product 1 leads to proteolytic product 2. 5. Proteolytic product 1 has a greater mobility in cellulose acetate electrophoresis at pH8 and binds more strongly to DEAE-cellulose than does native enzyme; the converse is true for proteolytic product 2. 6. Proteolytic product 1 is a tetramer with a monomer Mr about 74 300; proteolytic product 2 is also a tetramer. 7. Native enzyme can only be prepared in the presence of proteinase inhibitors; partial purifications based on simple fractionation of crude mucosal extracts in the absence of proteinases inhibitors contain proteolytic product 2 as the main component and proteolytic product 1 together with little native enzyme. 8. Purified native mucosal phosphofructokinase displayed little co-operativity with respect to fructose 6-phosphate at pH 7.0 and was only weakly inhibited by ATP.

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STUDIES ON THE DISTRIBUTION AND KINETICS OF THE ALKALINE PHOSPHATASE OF RAT SMALL INTESTINE

Canadian Journal of Biochemistry and Physiology ◽

10.1139/o59-076 ◽

1959 ◽

Vol 37 (5) ◽

pp. 699-709 ◽

Cited By ~ 15

Author(s):

Eugenie Triantaphyllopoulos ◽

Jules Tuba

Keyword(s):

Alkaline Phosphatase ◽

Small Intestine ◽

Specific Activity ◽

Supernatant Fraction ◽

Magnesium Ion ◽

Rat Small Intestine ◽

Albino Rat ◽

Michaelis Constants ◽

Intestinal Enzyme ◽

Kinetics Of

Alkaline phosphatase activity was demonstrated throughout the entire length of the small intestine of the albino rat and the relative amounts present seemed to decrease exponentially from the pylorus to the ileocolic valve. All subcellular fractions of intestinal homogenates were found to hydrolyze sodium β-glycero-phosphate. The distribution of activity of the enzyme was as follows: "microsomes", about 76%; nuclei, 10%; mitochondria, 8%; and in the nongranular, supernatant fraction, 9%. The specific activity for these fractions was: 52, 3, 10, and 3, respectively. The effects of the time of incubation, pH of the hydrolytic mixture, and the concentration of the enzyme were similar in all fractions. For the enzyme in the various fractions slight differences were observed in the values of the Michaelis constants, and in the degree of activation by magnesium ion. These variations may be explained on the basis of differences in the accessibility of substrate and magnesium ion to the enzymes in the various fractions. The finding that the "microsomes" contained the highest levels of alkaline phosphatase suggests that this intestinal enzyme is produced almost entirely by these submicroscopic particles.

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