Abstract
A comparison has been made of the milk and adipose tissue triglycerides of rabbits and guinea pigs provided with one diet and of rats and mice provided with another. Both intact triglycerides and component fatty acids were analyzed by gas-liquid chromatography. Good correlation of the data obtained by the two techniques was obtained by calculating the average chain length of the fatty acid moieties. Little difference was found in the triglyceride composition of the adipose tissue of the different species. However, wide variation in the triglyceride composition of the milk was found between the species: the average fatty acid chain length in milk was 11.7 for rabbits, 14.2 for rats, 15.3 for mice, and 17.2 for guinea pigs. The corresponding values for adipose tissue were in the range 16.9-17.4 in all animals. The significance of enzymes that synthesize short-chain fatty acids in mammary gland is discussed.
Highlights
Little difference was found in the triglyceride composition of the adipose tissue of the different species
SOME INFORMATION [1,2,3,4,5,6] is available on the fatty acid composition of rodent milk, little is known of the composition of the intact triglycerides, which we have analyzed by gas-liquid chromatography (GLC)
Sample deterioration could be readily detected by changes in the pattern of intact triglycerides determined by GLC
Summary
Guinea pigs, and mice were given an intraperitoneal injection of oxytocin (0.4 IU/kg) 20 min before they were killed by cervical dislocation. Intact triglycerides were analyzed by GLC immediately after extraction and purification. Sample deterioration could be readily detected by changes in the pattern of intact triglycerides determined by GLC. To confirm completion of methanolysis, we subjected the mixtures produced from cow's milk triglycerides to GLC under conditions appropriate to intact glycerides (15 ). Dietary fatty acids were obtained by saponification of samples of the diets with ethanolic NaOH under reflux for 8 hr, filtration of the mixture through glass wool, acidification to pH 2 with concentrated hydrochloric acid, and extraction of the free acids with n-hexane. GLC of the methyl esters of fatty acids was carried on a Pye Panchromatograph equipped with 152 X 0.65 cm columns of 10% polyethylene glycol adipate or 10%. While chromatography on polyethylene glycol adipate separated mono-, di-, and triunsaturated fatty acids, Apiezon L separateed saturated and monounsaturated acids and the combination of the results enabledeach sample to be completelyanalyzed.
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