Thromboxane synthesis inhibition and postprandial intestinal hyperemia and oxygenation

1986 ◽  
Vol 250 (1) ◽  
pp. G64-G69
Author(s):  
M. J. Mangino ◽  
C. C. Chou
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Glucose Absorption ◽  
Nutrient Absorption ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Synthesis Inhibitor ◽  
Anesthetized Dogs ◽  
Intestinal Glucose Absorption ◽  
Induced Changes

The effects of imidazole and U-63557A (Upjohn), inhibitors of thromboxane synthesis, on food-induced changes in intestinal blood flow and oxygen uptake were determined in the jejunum of anesthetized dogs. Intra-arterial (5.0 mg/min ia) infusions of imidazole had no effect on the postprandial intestinal hyperemia but significantly potentiated food-induced increases in oxygen uptake via enhanced oxygen extraction. Furthermore, imidazole had no effect on intestinal glucose absorption. The selective thromboxane synthesis inhibitor U-63557A (5 mg/kg iv) also enhanced oxygen uptake during nutrient absorption and had no effect on the hyperemia or glucose absorption. Our study indicates that inhibition of thromboxane synthesis has no effect on either resting intestinal blood flow or postprandial intestinal hyperemia but significantly enhances postprandial oxygen extraction and uptake. The potentiation of the food-induced increases in oxygen uptake by imidazole and U-63557A appears not to be related to glucose absorption. Endogenous thromboxane therefore appears to inhibit oxygen uptake more than blood flow, and yet does not affect glucose absorption during nutrient absorption.

Time course of jejunal blood flow, O2 uptake, and O2 extraction during nutrient absorption

1984 ◽  
Vol 247 (3) ◽  
pp. H395-H402 ◽  
Author(s):  
S. P. Sit ◽  
C. C. Chou
Keyword(s):  
Blood Flow ◽  
Bile Flow ◽  
Time Course ◽  
Glucose Absorption ◽  
Significant Rise ◽  
Nutrient Absorption ◽  
O2 Uptake ◽  
O2 Extraction ◽  
Steady Level ◽  
Anesthetized Dogs

Experiments were performed on anesthetized dogs to determine whether responses of jejunal blood flow, arteriovenous O2 difference, O2 uptake (VO2), and glucose absorption to luminal placement of predigested food or glucose would change with time during 30- and 60-min placement periods and to determine whether bile alters the responses. During the initial 15 min, food, glucose, food plus bile, and glucose plus bile produced a 13, 10, 51, and 30% increase in flow, respectively. During the next 15 min, flow returned to control levels, while arteriovenous O2 difference significantly increased with food or glucose; with glucose plus bile, flow decreased to 28% above control. In the case of food plus bile, flow decreased to 26% above control at 30 min and returned to control 50 min after placement. Despite the fluctuation in flow, the increase in VO2, and glucose absorption stayed at a steady level throughout the entire placement period. Bile significantly enhanced the increases in both flow and VO2 produced by food or glucose, prolonged the hypermia, delayed the significant rise in arteriovenous O2 difference, and had no effect on glucose absorption. In conclusion, the relative contributions of blood flow and O2 extraction to the enhanced VO2 produced by luminal food and glucose change with time, and bile significantly alters the magnitude or time course of changes in the above three variables.

Influence of luminal nutrient composition on hemodynamics and oxygenation in developing intestine

1992 ◽  
Vol 263 (2) ◽  
pp. G254-G260 ◽  
Author(s):  
K. D. Crissinger ◽  
D. L. Burney
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Vascular Resistance ◽  
Corn Oil ◽  
Age Groups ◽  
Older Age ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Age Related

Age-related differences in the intestinal hemodynamic and oxygenation responses to carbohydrate, protein, and lipid were studied in 1-day-, 3-day-, 2-wk-, and 1-mo-old piglets. A branch of the mesenteric vein draining an isolated loop of jejunoileum was used to measure intestinal blood flow, arteriovenous oxygen content difference, and venous and capillary pressure and to calculate oxygen uptake and vascular resistance. Fractionated intestinal flow was measured with radiolabeled microspheres. Measurements were made before and after luminal placement of either 5% glucose, 2.3% casec, or 5% corn oil. In 1-day-old animals, unlike all older age groups, total intestinal blood flow and vascular resistance were unchanged by any nutrient. Fractionated flow to the mucosa/submucosa levels did, however, increase in the intestine of 1-day-old piglets to a similar extent as that in older age groups. Placement of lipid or protein into the lumen led to increased oxygen uptake in all age groups, whereas carbohydrate absorption resulted in no increase in intestinal oxygen consumption in 1- and 3-day-old animals. In 1-day-olds, the increased oxygen consumption was achieved by enhanced oxygen extraction with no change in total blood flow, whereas all other groups demonstrated increases in blood flow and/or oxygen extraction. Compared with a mixed meal, oxygen consumption was not significantly greater for an individual nutrient component.

Effects of varying hematocrit on intestinal oxygen uptake in neonatal lambs

1985 ◽  
Vol 248 (4) ◽  
pp. G432-G436 ◽  
Author(s):  
I. R. Holzman ◽  
B. Tabata ◽  
D. I. Edelstone
Keyword(s):  
Blood Flow ◽  
Anaerobic Metabolism ◽  
Lactate Production ◽  
Oxygen Availability ◽  
Intestinal Blood Flow ◽  
Oxygen Extraction ◽  
Base Line ◽  
Wide Range ◽  
O2 Extraction ◽  
Neonatal Lambs

We chronically catheterized 15 newborn lambs (9.5 +/- 2.8 days) and measured intestinal blood flow (Qi) by the radionuclide microsphere technique at hematocrit levels ranging from 10 to 55%. Seven animals were made progressively anemic and eight polycythemic by means of exchange transfusions. Using the Fick principle, we calculated intestinal oxygen delivery (Di o2), oxygen consumption (Vi o2), and oxygen extraction. Initial base-line values were Qi = 195.5 ml . min-1 . 100 g intestine-1, Di o2 = 22.1 ml . min-1 . 100 g-1, Vi o2 = 4.8 ml . min-1 . 100 g-1, and O2 extraction = 22.5%. As the hematocrit was lowered, Di o2 decreased and O2 extraction increased and vice versa when the hematocrit was raised. Vi o2 remained constant, but Qi did not correlate with changes in hematocrit. However, intestinal blood flow, as a percent distribution of total blood flow, decreased with lower hematocrit levels. At no time was there any evidence of anaerobic metabolism as measured by excess lactate production. Our data indicate that the intestines of neonatal lambs are capable of maintaining their metabolic needs over a wide range of oxygen availability induced by a changing hematocrit. The primary mechanism is through alteration of oxygen extraction. Within the range of our experiments, no critically low oxygen availability was attained at which anaerobic metabolism became significant.

Regulation of jejunal blood flow and oxygenation during glucose and oleic acid absorption

1985 ◽  
Vol 249 (6) ◽  
pp. G691-G701 ◽  
Author(s):  
C. C. Chou ◽  
R. A. Nyhof ◽  
P. R. Kvietys ◽  
S. P. Sit ◽  
R. H. Gallavan
Keyword(s):  
Blood Flow ◽  
Oleic Acid ◽  
Glucose Absorption ◽  
O2 Uptake ◽  
Acid Absorption ◽  
Resistance Vessels ◽  
Permeability Surface ◽  
Anesthetized Dogs ◽  
Area Product ◽  
Oxygen Difference

To differentiate the mechanisms whereby actively absorbed glucose and passively absorbed oleic acid increase blood flow and oxygen uptake during their absorption, the effects of these two nutrients on jejunal blood flow, arteriovenous oxygen difference [(a-v)O2], O2 uptake, absorption, rubidium extraction, and capillary permeability-surface area product (PS) were compared in anesthetized dogs. Oleic acid (37 mM) produced significantly greater hyperemia (+28.2%) than glucose (270 mM) did (+12.5%). As estimated by (a-v)O2, tissue oxygen extraction was decreased by oleic acid (-12%) but increased by glucose (+6.5%); the increases in O2 uptake by these two nutrients did not differ significantly. Glucose absorption was accompanied by an increase in rubidium extraction and capillary PS (+11.3%), whereas oleic acid absorption was not. Unlike glucose, intra-arterial infusion of oleic acid decreased vascular resistance and increased blood flow equally to the mucosa and muscularis layers. A significant relation existed between oleic acid absorption and blood flow but not between glucose absorption and blood flow. The enhancement of glucose-induced hyperemia by bile was not related to glucose absorption. Unmasking of oleic acid-induced hyperemia by bile is unrelated to oleic acid absorption but is related to solubility of oleic acid in aqueous solution. The above findings suggest that glucose absorption affects both resistance and exchange vessels, whereas oleic acid absorption affects primarily resistance vessels.

Differences between the effects of noradrenaline and the β-adrenoceptor agonist BRL 28410 in brown adipose tissue and hind limb of the anaesthetized rat

1986 ◽  
Vol 64 (8) ◽  
pp. 1111-1114 ◽  
Author(s):  
Peter L. Thurlby ◽  
Rodney D. M. Ellis
Keyword(s):  
Blood Flow ◽  
Adipose Tissue ◽  
Oxygen Uptake ◽  
Brown Adipose Tissue ◽  
Oxygen Delivery ◽  
Hind Limb ◽  
Oxygen Extraction ◽  
Whole Body ◽  
Adrenoceptor Agonist ◽  
Brown Adipose

In mature (450–600 g) 21 °C-acclimated male rats, anaesthetized with urethane, blood flow (measured by the radioactive microsphere technique) to brown adipose tissue (BAT) was determined during the infusion of the β-adrenoceptor agonist BRL 28410 or noradrenaline bitartrate at doses chosen to give similar increases in whole body oxygen uptake. Blood flow to BAT during BRL 28410 infusion was only about one third of that found during noradrenaline infusion although increases in whole body thermogenesis were similar (55 and 77% for BRL 28410 and noradrenaline, respectively). This suggests that BAT may be less involved in the thermogenic response to BRL 28410 than to noradrenaline. In a separate experiment using slightly smaller rats (350–500 g) hind limb oxygen uptake was measured in situ using a venous bypass preparation. BRL 28410, at a dose having a maximum effect on whole body thermogenesis (53% increase), had no effect on oxygen delivery to the hind limb but significantly increased oxygen extraction by 33% (p < 0.001). In contrast, noradrenaline, also at a dose that maximally increased whole body thermogenesis, led to a 35% decrease in oxygen delivery to the hind limb and no change in oxygen extraction. For the thermogenic β-agonist BRL 28410 the hind limb, and presumably muscular tissue in general, may be contributing to thermogenesis.

Influence of blood rheology on intrarenal blood flow distribution

1976 ◽  
Vol 230 (5) ◽  
pp. 1448-1454 ◽  
Author(s):  
KM McDonald
Keyword(s):  
Blood Flow ◽  
Arterial Pressure ◽  
Flow Distribution ◽  
Blood Rheology ◽  
Blood Flow Distribution ◽  
Cortical Level ◽  
Arteriolar Resistance ◽  
Anesthetized Dogs ◽  
Intrarenal Blood Flow ◽  
Induced Changes

This study examined the effects of hematocrit and colloid-induced changes in blood rheology on renal blood flow (RBF) distribution. Blood viscosity, measured by coneplate viscometry, was raised 65% in anesthetized dogs either by increasing hematocrit or giving isoncotic dextran 500. Blood volume was kept constant and arterial pressure was unchanged. An increase in hematocrit caused either no change in RBF or a slight increase at each cortical level (zones 1-4). However, dextran hyperviscosity caused decreases in all four zones, the most pronounced in zone 1 (8.03-5.19 ml min(-1) g(-1)) and the least in zone 4 (1.63-1.46 ml min(-1) g(-1)). These data suggest either that increased hematocrit has less effect on "apparent viscosity" of blood within the kidney than does plasma colloid or that increased hematocrit causes renal vasodilatation while colloid hyperviscosity does not cause it. Since GFR remained constant in both types of hyperviscosity, it is possible that GFR is the autoregulated variable and the observed changes in RBF distribution and vascular resistance resulted from the changes in afferent and efferent arteriolar resistance required to preserve GFR.

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