Hepatic secretion of lipids and apolipoproteins in rats fed soybean phospholipid and soybean oil.

Dietary phospholipid (PL) containing phosphatidylethanolamine alters serum lipoproteins in rats. To clarify the underlying mechanism for the alteration of serum lipids and apolipoproteins, secretions of lipids and apolipoproteins from isolated perfused livers in rats fed soybean PL or soybean oil were compared in this study. Soybean PL significantly decreased the rates of accumulation of apolipoprotein A-I (apoA-I) and cholesterol in the liver perfusate. The secretion of newly synthesized apoA-I labeled with [3H]lysine into the perfusate also significantly decreased in rats fed soybean PL. The secretion patterns of triglyceride and apolipoproteins other than apoA-I were similar for rats fed either diet. Constant infusion of oleic acid into the liver perfusion medium did not alter the response of the secretion of lipids and apolipoproteins to soybean PL feeding. In rats injected with Triton WR-1339, concentrations of serum triglyceride and high-molecular-weight apoB at 20 hours after injection were significantly increased by soybean PL feeding, whereas until 2 hours postinjection the accumulation of serum triglyceride was similar for rats fed either diet. Thus, soybean PL affects not only secretion of hepatic lipoproteins but also metabolism of triglyceride-rich lipoproteins derived from the liver.