Distribution of radioactivity of intraperitoneally administered 14C-leucine and 14C-alanine in tissues of suckling lambs.

14C-labelled leucine and alanine were administered intraperitoneally to suckling male lambs aged 30. The distribution of radioactivity was investigated in the liver, heart, quadriceps femoris muscle, subcutaneous adipose tissue, skin and expired air. Most of the radioactivity (per 1 g of dry tissue) was found in proteins of liver, followed by proteins of the heart, skin, muscle and adipose tissue. The radioactivity found in lipids and glycogen was much lower, with the exception of high radioactivity of leucine-derived lipids of the adipose tissue. Incorporation of alanine into proteins was lower than that of leucine. On the other hand, more alanine was oxidized to CO2 than leucine.