Recycling of Intravenously Injected Palmitic Acid‐l‐C¹⁴ as Esterified Fatty Acid in the Plasma of Rats and Turnover Rate of Plasma Triglycerides

The disappearance of injected palmitic acid‐l‐C 14 from plasma in the rat was followed. It was found that part of the complexity of the disappearance curves in experiments with starving rats resulted from exchange of non‐esterified fatty acids (NEFA) between plasma and adipose tissue. The content of NEFA in adipose tissue was considerably higher in starving than in glucose fed rats. After a time lag part of the injected palmitic acid returned to plasma incorporated in triglycerides (TG) in starving as well as in glucose fed rats. The specific activity relationships between plasma TG and NEFA suggested that most of the NEFA in plasma was derived from plasma TG in the glucose fed rats and part of it in the starving rats. The ratio between the specific activity of plasma TG and of liver TG suggested that all plasma TG might be derived from liver TG in glucose fed rats. This was more uncertain in starving rats. The half life of endogenous plasma TG was found to vary between 3.0 and 8.5 minutes.