Some Conditions Affecting the Maintenance of a Steady Lymphatic Absorption of Fat

Shepherd, P. A.; Simmonds, W. J.

doi:10.1038/icb.1959.1

Cited by 88 publications

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“…The present experiments in which the rate of removal of fat from the intestinal lumen was measured, may be compared with a previous series in which the rate of transfer of absorbed fat to the lymph was determined [Shepherd and Simmonds, 1959]. The units of measurement were differentsaponifiable fat for absorption from the lumen and esterified fat for output in lymph.…”

Section: Hrmentioning

confidence: 89%

Absorptive Capacity and Intestinal Motility in Unanæsthetized Rats During Intraduodenal Infusion of Fat

Bennett

Simmonds

1962

Exp Physiol

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Emulsified coconut oil mixed with unabsorbable, water soluble reference material, polyethylene glycol (PEG) was given to unanaesthetized rats in restraint cages. Complications due to variable stomach emptying were evaded by steady infusion through previously implanted duodenal cannulae. Recoveries of fat in rats killed after 2-hr. and 4-hr. infusions showed a steady rate of absorption with a capacity limited to about 100 mg. coconut oil per hr. Recoveries of PEG showed an increased rate of propulsion, particularly through the distal small intestine, in the presence of either coconut or cottonseed oil. Fat: PEG ratios in proximal and distal halves of the small intestine were consistent with predominantly distal absorption of fat until absorptive capacity was nearly saturated, when there was evidence that the reference substance moved ahead of the fat.THE depressant effect of fat on stomach emptying complicates the interpretation of gastric test meals. For example, when increasing doses of fat were given to rats by mouth, the absorptive capacity of the small intestine could not be determined, because the rate of delivery of fat by the stomach imposed a limit on the rate of absorption [Aberdeen, Shepherd and Simmonds, 1960]. The possible effect of the fat itself on the progress of an unabsorbable marker through the small intestine could not be distinguished from changes attributable to slower stomach emptying. In the experiments reported in this paper such complications were avoided by a steady infusion of the test meal directly into the duodenum in unanaiesthetized rats. METHODSGeneral Procedure.-Male albino rats weighing from 220 to 280 g. were used. Two days before experiment, under ether anaisthesia a very flexible silicone elastomer tube, outer diameter 0 5 mm., was passed through an incision in the stomach into the duodenum so that the tip lay about 2 cm. distal to the pyloric sphincter. The tube was anchored by fine sutures near the tip and where it passed through the stomach wall. The free end was brought through the skin at the back of the neck and plugged. After closure of wounds the animals were returned to separate cages, without food, but with 5 per cent glucose in water ad lib. On the night before experiment, animals were lightly anaesthetized and placed in a restraining cage [Bollmann, 1948]. On the following morning a small priming dose of emulsified oil, 0 05 ml., was given through the duodenal tube and washed down with 0-2 ml. 0 9 per cent NaCl solution. After 10 min., the test meal was infused at a constant speed for either 2 or 4 hr.The test meal was usually a mixture of emulsified coconut oil, polyethylene glycol (PEG) of mol. wt. 3000-4000 and 0 9 per cent NaCl solution. A proprietary emulsion,

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Section: Hrmentioning

confidence: 89%

Absorptive Capacity and Intestinal Motility in Unanæsthetized Rats During Intraduodenal Infusion of Fat

Bennett

Simmonds

1962

Exp Physiol

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“…This requires cannulation of the lymphatic duct and insertion of a duodenal cannula for infusion of radiolabeled Ch. In our in situ experimental system, mice were anesthetized during the experiments, which allowed hourly collection of fresh lymph samples without the effects of stress on the animals such as could be induced by restraining cages (89,90). A critical factor in the validity of the Ch absorption measurement by lymph fistula is maintenance of constant lymph flow during the study.…”

Section: Reevaluation Of Methods For Measurement Of Intestinal Ch Absmentioning

confidence: 99%

Measurement of intestinal cholesterol absorption by plasma and fecal dual-isotope ratio, mass balance, and lymph fistula methods in the mouse: an analysis of direct versus indirect methodologies

Wang

Carey

2003

Journal of Lipid Research

133

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The rate of intestinal cholesterol (Ch) absorption is an important criterion for quantitation of Ch homeostasis. However, studies in the literature suggest that percent Ch absorption, measured usually by a fecal dual-isotope ratio method, spans a wide range, from 20% to 90%, in healthy inbred mice on a chow diet. In the present study, we adapted four standard methods, one direct (lymph collection) and three indirect (plasma and fecal dual-isotope ratio, and sterol balance) measurements of Ch absorption and applied them to mice. Our data establish that all methodologies can be valid in mice, with all methods supporting the concept that gallstone-susceptible C57L mice absorb significantly more Ch (37 ؎ 5%) than gallstone-resistant AKR mice (24 ؎ 4%). We ascertained that sources of error in the literature leading to marked differences in Ch absorption efficiencies between laboratories relate to a number of technical factors, most notably expertise in mouse surgery, complete solubilization and delivery of radioisotopes, appropriate collection periods for plasma and fecal samples, and total extraction of radioisotopes from feces. We find that all methods provide excellent interexperimental agreement, and the ranges obtained challenge previously held beliefs regarding the spread of intestinal Ch absorption efficiencies in mice. The approaches documented herein provide quantifiable methodologies for exploring genetic mechanisms of Ch absorption, and for investigating the assembly and secretion of chylomicrons, as well as intestinal lipoprotein metabolism in mice. The small intestine is the organ uniquely responsible for partial absorption of both dietary and biliary cholesterol (Ch), and plays a major role in regulation of wholebody Ch balance (1-3). Accurate and precise measurements of intestinal Ch absorption is one of the basic requirements for quantitation of Ch homeostasis as well as for ascertaining genetic variations and drug effects. Presently, there are three indirect methods available for measuring Ch absorption. Of these, the simplest is the plasma dual-isotope ratio method introduced by Zilversmit (4), recently modified by us for the mouse (5, 6). The method is based on the simultaneous ig and iv administration of [ 3 H]Ch and [ 14 C]Ch and measurement of plasma Ch isotope ratios at a set point in time: by definition, it assumes "100% absorption" of the iv dose. The most frequently employed method in the literature is the fecal dual-isotope ratio method (7), which is based on the administration of a single oral dose of radiolabled Ch and a nonabsorbed radiolabled phytosterol, such as ␤ -sitosterol (7,8) or sitostanol (9), as reference marker. The measurement is critically dependent on an accurate assessment of the ratios of excreted radioactivities of the two isotopes and their bacterial metabolites in feces. In a metabolic steady state, the sterol balance method (10-12) estimates the mass absorption of exogenous Ch based on the difference between dietary Ch and its fecal excretion. The measurement...

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“…Emulsified oleic acid was as well absorbed in bile fistula animals as in controls and the return or removal of taurocholate did not affect the output of esterified fat in the lymph. These results do not support a defect in epithelial re-esterification of fatty acids in the absence of bile.WHEN fat is infused at a steady rate directly into the duodenum of unanawsthetized rats, within a few hours the output of fat in the thoracic duct lymph reaches a plateau mirroring the absorption of fat [Shepherd and Simmonds, 1959]. When fat absorption is altered after a steady state has been established, the change is soon reflected in the lymphatic output of fat [Bennett et al, 1962] and so each experiment provides its own control period.…”

mentioning

confidence: 99%

“…WHEN fat is infused at a steady rate directly into the duodenum of unanawsthetized rats, within a few hours the output of fat in the thoracic duct lymph reaches a plateau mirroring the absorption of fat [Shepherd and Simmonds, 1959]. When fat absorption is altered after a steady state has been established, the change is soon reflected in the lymphatic output of fat [Bennett et al, 1962] and so each experiment provides its own control period.…”

mentioning

confidence: 99%

The Effect of Bile Salts on the Lymphatic Absorption by the Unanæsthetized Rat of Intraduodenally Infused Lipids

Morgan

1964

Exp Physiol

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Emulsified and unemulsified fat was infused intraduodenally at a steady rate in unanaesthetized rats with lymph fistulhe. The output of esterified fat in the lymph reached a steady state which was considered to mirror fat absorption from the lumen. In animals which also had bile fistulae the effect of addition or removal of sodium taurocholate was measured.Unemulsified olive oil or oleic acid and mono-olein sol was poorly absorbed in the absence of bile. Emulsified olive oil was better, but still incompletely, absorbed. In all these cases the addition of sodium taurocholate increased the absorption to that found in control animals with normal bile flow. Emulsified oleic acid was as well absorbed in bile fistula animals as in controls and the return or removal of taurocholate did not affect the output of esterified fat in the lymph. These results do not support a defect in epithelial re-esterification of fatty acids in the absence of bile.WHEN fat is infused at a steady rate directly into the duodenum of unanawsthetized rats, within a few hours the output of fat in the thoracic duct lymph reaches a plateau mirroring the absorption of fat [Shepherd and Simmonds, 1959]. When fat absorption is altered after a steady state has been established, the change is soon reflected in the lymphatic output of fat [Bennett et al., 1962] and so each experiment provides its own control period. This technique has been used to determine the effect of bile salts on the absorption of emulsified and unemulsified olive oil and oleic acid and of a mono-olein sol in rats with external bile fistulae. The aim was to evaluate the relative importance of the effect on lipolysis and on dispersion of triglyceride and digestion products in the lumen, on re-esterification during passage through the epithelium [Dawson and Isselbacher, 1960] and on the pathway of absorption [Borgstrom, 1953]. METHODSOperative Procedures-Male albino rats weighing 200-220 g. were fasted overnight. Under ether anaesthesia a thoracic duct fistula was established in each rat [Bollman et al., 1948] and at the same time a fine silicone rubber cannula was introduced into the duodenum through a fundal incision in the stomach. The tip of the duodenal * This work was carried out with the aid of grants from the National Health an(d Medical Research Council, Canberra, and the Medical Researchl Grants Committee, The

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Some Conditions Affecting the Maintenance of a Steady Lymphatic Absorption of Fat

Cited by 88 publications

References 0 publications

Absorptive Capacity and Intestinal Motility in Unanæsthetized Rats During Intraduodenal Infusion of Fat

Absorptive Capacity and Intestinal Motility in Unanæsthetized Rats During Intraduodenal Infusion of Fat

Measurement of intestinal cholesterol absorption by plasma and fecal dual-isotope ratio, mass balance, and lymph fistula methods in the mouse: an analysis of direct versus indirect methodologies

The Effect of Bile Salts on the Lymphatic Absorption by the Unanæsthetized Rat of Intraduodenally Infused Lipids

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