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Biomedical subjects

B Borgström

Publications and source records attributed to B Borgström.

At least 109 records · Page 6Linked to original sources
PubMed1968

Quantitative aspects of the intestinal absorption and metabolism of cholesterol and beta-sitosterol in the rat.

The quantitative aspects of intestinal absorption and metabolism of cholesterol and -sitosterol have been studied in the rat after a single feeding of radioactive sterols. When increasing amounts of cholesterol were fed in a constant amount of triolein, the percentage absorbed decreased only gradually and the total amounts absorbed increased to a maximum. Solubility in the fat component fed is one limiting factor in the absorption of cholesterol. At the lowest dose fed, only about 50% of dietary cholesterol was absorbed even though increasing the amount fed led to a 10- to 15-fold increase in total absorption. Sitosterol, when fed in triolein, was absorbed in amounts only one-tenth of the corresponding dose of cholesterol. Intestinal transit studies indicate that the distinction between sitosterol and cholesterol, when fed together, took place during the process of uptake into the intestinal mucosa. Once taken up by the intestinal mucosal cells, cholesterol and sitosterol did not differ in their subsequent rate of transit out of the mucosal cell. Feeding sitosterol with cholesterol seems to have the same effect on cholesterol absorption as feeding the same additional dose of cholesterol, the difference being that sitosterol is taken up by the intestinal wall in amounts only one-tenth to one-fifth of that of cholesterol. The rapid and complete absorption of the triglyceride fat and the subsequent transit of the intestinal content to the large intestine are most probably important factors in the determination of the extent of absorption of nonglyceride fat. The mechanism behind the difference in extent of absorption of the closely related sterols is not explained.

Animals↗
PubMed1968

Absorption and lymphatic transport of cholesterol in the rat.

Rats with thoracic duct fistulae were fed triolein and triolein containing various amounts of labeled cholesterol. The analysis of the lymph lipids gave the following results. In the fasting state the cholesterol transported via the thoracic duct was 0.87 micromole/hr. Feeding 800 micromoles of triolein gave a maximum rate of transport of cholesterol of 1.65 micromoles/hr. Addition of cholesterol to the triolein further increased the cholesterol transport to a maximal rate of almost 5 micromoles/hr when 50 micromoles of cholesterol were fed per 800 micromoles of triolein. The exogenous fraction of the cholesterol transported increased linearly with increasing cholesterol load, constituting at the highest dose almost 90% of the total cholesterol transported. An almost constant fraction (about 0.4) of the dietary cholesterol was recovered in the thoracic duct lymph in 24 hr irrespective of the dose fed, from a trace up to 100 micromoles in 800 micromoles of triolein. Cholesterol absorption has the characteristics of a passive diffusion process.

Absorption↗
PubMed1967

Partition of lipids between emulsified oil and micellar phases of glyceride-bile salt dispersions.

The composition of the emulsified oil and of the micellar phases obtained when a glyceride-fatty acid mixture is dispersed in bile salt solution has been defined. The micellar phase in equilibrium with the emulsified oil phase was obtained by filtration through Millipore filters. The behavior of different lipids in such systems was defined as the partition ratio, micellar/emulsified oil phase (m/o). Partition of fatty acids was found to be strongly dependent on the chain length of the fatty acid and the pH of the dispersion. The curve for partition against pH for oleic acid was interpreted to show a pK(a) for oleic acid in bile salt solution of approximately 7. The partition between micellar and oil phases is given for a series of lipids of different polarity. No significant difference in behavior was found for cholesterol and sitosterol. A relationship was found between the partition m/o and filtration rates through a Millipore filter in micellar solution. The lower the partition coefficient the lower was the rate of filtration. The results obtained are discussed in relation to the mechanism of absorption of fat from the small intestine.

Bile Acids and Salts↗