THE UPTAKE FROM THE BLOOD OF TRIGLYCERIDE FATTY ACIDS OF CHYLOMICRA AND LOW-DENSITY LIPOPROTEINS BY THE MAMMARY GLAND OF THE GOAT

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Abstract
Arteriovenous measurements were made across the mammary glands of lactating goats to discover which fractions of the plasma lipids provide fatty acids for the formation of milk fat. Pronounced arteriovenous differences were found in the triglyceride fatty acids of chylomicra and d < 1-019 low-density lipoproteins. The fatty acids taken up from this fraction were principally palmitic acid and stearic acid. No significant arteriovenous difference was found in a non-lactating goat. Arteriovenous measurements of free fatty acids showed that they were not taken up by the gland in amounts comparable with those of the triglyceride fatty acids. In the goat a large part, and possibly all, of the fatty acids of milk that come from the blood lipids are derived from the triglycerides of the chylomicra and d 1[center dot]019 low-density lipoproteins. The activity of clearing factor lipase in the mammary venous blood of lactating goats was over 3 times that in the arterial. In lactating goats pronounced arteriovenous differences were found in D-[beta]-hydroxybutyrate, but not in acetoacetate. Arteriovenous measurements of the free glycerol of blood showed that this fraction could not provide a significant part of the glycerol of milk fat.