The excretion of 14CO2 during the continuous intravenous infusion of NaH14CO3 in unanaesthetized rats

Morris, B; Simpson‐Morgan, M. W.

doi:10.1113/jphysiol.1963.sp007291

Cited by 22 publications

(19 citation statements)

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“…It can be inferred that the term 0-58e0 094t, which delays the excretion of the 14CO2, is associated with the excretion of C02 from the bicarbonate pools. A component similar to this term appeared in the 14C02 excretion curve when rats were infused continuously with NaH14C03 (Morris & Simpson-Morgan, 1963). However, the mean circulating half-life of infused chylomicrons is also of the same order as this term and it too will feature in this component.…”

Section: Rate Of Infusionmentioning

confidence: 90%

The oxidation of continuously infused chylomicron fatty acids by unanaesthetized rats

Morris¹,

Simpson‐Morgan²

1963

The Journal of Physiology

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Long-chain fatty acids are absorbed from the gut and transported in the thoracic duct lymph in the form of chylomicrons. More than 90 % of the fatty acids in these particles are present as triglycerides. In the rat given a meal of fat, absorption occurs over a period of several hours and under normal circumstances chylomicrons are entering the circulation continuously.By collecting chyle from rats with thoracic-duct fistulae it is possible to obtain a lipid substrate in a physiological form which can be introduced directly into the blood stream in significant amounts. In most experiments in which the oxidation of '40-labelled chylomicron fat has been studied the fat was given as a single intravenous injection (French & Morris, 1958;Morris, 1958;Bragdon, 1958;Frederickson, McCollester & Ono, 1958). There are objections to this method of administration both from the physiological viewpoint and from the subsequent interpretation of the excretion patterns of 14C(02.In order to study the oxidation of chylomicron fatty acids under conditions which simulate their normal mode of entry into the circulation, a series of experiments has been carried out in rats in which 14C-labelled rats' chylomicrons were infused continuously into the blood stream. The rates of oxidation of 14C-labelled palmitic, oleic and linoleic acids have been compared by incorporating these fatty acids into chylomicrons. The oxidation of each labelled fatty acid and the amount of radioactive and total lipid present in the liver at the end of the infusion were examined over a wide range of rates of infusion of total fatty acid. The effect of these various infusion rates on the circulating level of esterified fatty acids in the plasma was also examined. METHODSCollecion and preparation of chylomicrons. Labelled and unlabelled chylomicrons were obtained from rats with thoracic-duct fistulae. A gastrostomy tube was inserted in the stomach at the sane time as the thoracic duct was cannulated. The rats were given 'triolein' (laboratory reagent, British Drug Houses) through the gastrostomy tube and the chyle was

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Section: Rate Of Infusionmentioning

confidence: 90%

The oxidation of continuously infused chylomicron fatty acids by unanaesthetized rats

Morris¹,

Simpson‐Morgan²

1963

The Journal of Physiology

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“…6. Dilantin administered intraperitoneally to fed and fasted rats caused a significant increase in plasma FFA.…”

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confidence: 96%

“…The combined effects of Dilantin and hormones upon rat plasma FFA concentrations are shown in Table I Evidence has been presented that triglyceride is mobilized from adipose tissue in the form of FFA which circulates as an albumin-FFA complex ( 5,6). The adipokinetic action of hormones has been reviewed by Vaughan (7) and Rudman (8).…”

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confidence: 99%

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Effects of Diphenylhydantoin upon the Plasma Free Fatty Acid Response Induced by Hormones.

Chung

1965

Experimental Biology and Medicine

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partially account for the observed difference between infused and expired carbon-14.About 33% of the radioactivity found in the urine was in the form of C02. However, identification of compounds containing the remaining radioactivity was not made. Rust et aZ (13) found radioactivity in urea of the urine of rats following injections of sodium bicarbonate-14.The close agreement between the half-life of blood CO:! and respiratory CO:! calculated from the exponential part of the curve ( Fig. 1 and 2 ) suggest that blood CO2 data may be used in studying oxidative rates of substrates. This would eliminate the respiratory stress of the animal due to the apparatus needed to collect expired air.The turnover rate was constant for the 3 experiments with a mean of 9.58 mecl/hr/kg of body weight. The mean CO2 space was 0.414 liter/kg body weight, which is about twice the extracellular volume. The amount of radioactivity found in the rumen would indicate that the rumen must be considered part of the C 0 2 space.Summary. The carbon dioxide pool system of sheep was evaluated by the constant infusion of sodium bicarbonate-C14 for a period of 4 hours. The specific activity of blood CO, plateaued during the final hour of infusion. Following infusion, the half-lives of blood and expired COs were 32.6 and 31 minutes, respectively. Mean turnover rate, turnover time and C 0 2 space were 9.58 meq/hr/ kg body weight, 46.8 minutes and 41.4% of body weight, respectively. Considerable radioactivity wits found in the rumen a t the end of the infusion period. These observations suggest a time of a t least 3 hours for complete labeling of the C 0 2 pool, of which the rumen is a part, and that blood C 0 2 data may be used as well as expired C02 data for substrate oxidation studies.

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“…Unlabelled chylomicrons and chylomicrons labelled with [14C]palmitic acid were collected from rats with thoracic duct fistulae which had been fed with olive oil. The chylomicrons were prepared for infusion as previously described (Morris & Simpson-Morgan, 1963 b). The chylomicrons were resuspended in electrolyte solution after ultracentrifugation.…”

Section: Introductionmentioning

confidence: 99%

The metabolism of chylomicron fatty acids by isolated rat heart‐lung preparations

Simpson‐Morgan¹

1968

The Journal of Physiology

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SUtMMARY1. An isolated rat heart-lung preparation is described. This preparation is perfused with the rat's own blood, in the absence of heparin or other anticoagulants, by the sustained efficient contractions of the heart. The preparation has only a small circulating blood volume and is stable for up to 3 hr.2. Chylomicrons which were infused continuously into the circulating blood of the heart-lung preparation were removed from the circulation.3.[14C]Palmitic acid incorporated into the chylomicrons was oxidized rapidly to CO2. Rates of oxidation of chylomicron fatty acids in excess of 3 mg/hr were measured and suggest that in the intact rat, the heart and lungs could account for up to 10 % of the chylomicron fatty acids oxidized.4. The infusion of glucose did not reduce the oxidation of the chylomicron fatty acids, whilst the infusion of sufficient quantities of chylomicrons in the absence of glucose spared some of the cardiac glycogen.

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The excretion of ¹⁴CO₂ during the continuous intravenous infusion of NaH¹⁴CO₃ in unanaesthetized rats

Cited by 22 publications

References 10 publications

The oxidation of continuously infused chylomicron fatty acids by unanaesthetized rats

The oxidation of continuously infused chylomicron fatty acids by unanaesthetized rats

Effects of Diphenylhydantoin upon the Plasma Free Fatty Acid Response Induced by Hormones.

The metabolism of chylomicron fatty acids by isolated rat heart‐lung preparations

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