Key result
Endogenous lipid contributes to the formation of VLDL particles in the jejunal mucosa of developing rats, whereas dietary triglycerides from suckling are needed for the formation of chylomicrons.
This preclinical study demonstrates that in developing rats, endogenous lipids drive VLDL formation while dietary triglycerides are required for chylomicron formation in the jejunal mucosa.
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Neonatal rat data on jejunal lipoproteins should not guide infant feeding; extends fetal observations but leaves human relevance open.
The jejunal mucosa of neonatal rats contains lipid particles of the same size, electron density and intracellular and extracellular distribution as particles identified by others in adult jejunum as lipoprotein particles. As in fetal jejunum obtained during the last three days of gestation, the jejunal mucosa of unsuckled newborn rats contains exclusively lipoprotein particles the size of very low density lipoproteins (VLDL). Within one day after initiation of suckling, there is in the mucosa a spectrum of lipoprotein particles ranging widely in size from those of VLDL particles to those of chylomicrons. These particles are seen in the endoplasmic reticulum and Golgi material of absorptive cells and within interepithelial cell spaces, the extracellular spaces of the lamina propria and lymphatic lacteals. VLDL-sized and chylomicron-sized particles are also seen, although in decreasing number, in the jejunal mucosa of 18-day-old suckling rats. However, in rats of comparable age, fasted for 48 or 72 hours, only VLDL-sized particles are seen in the jejunal mucosa. Ligation and transection of bile duct followed by fasting in rats of this age results in a marked decrease in the number of lipoprotein particles in absorptive cells. The results indicate that endogenous lipid contributes to the formation of VLDL particles whereas dietary triglycerides are needed for formation of chylomicrons.
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Mak et al. (1979) studied Postnatal developing rats. Suckling, fasting, and bile duct ligation vs. Unsuckled newborn rats and fetal rats was evaluated on Presence and size of lipoprotein particles in the jejunal mucosa. Endogenous lipid contributes to the formation of VLDL particles in the jejunal mucosa of developing rats, whereas dietary triglycerides from suckling are needed for the formation of chylomicrons.
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