Distribution of radioactive hemoprotein and CO-binding pigment in rough and smooth endoplasmic reticulum of rat liver

Abstract

The adminitration of radioactive δ-aminolevulinic acid (δ-ALA) to immature male rats leads to the incorporation of radioactivity into the hemoproteins of the rough and smooth endoplasmic reticulum of rat liver. Time-course studies on the rates of radioactive δ-ALA and leucine incorporation into rough and smooth endoplasmic reticulum suggest that apocytochrome may exist in liver microsomes. Studies on the decay of radioactive hemoprotein labeled with δ-ALA demonstrated a biphasic decrease of the radioactivity incorporated in both rough and smooth endoplasmic reticulum. The l 1 2 of the fast phase was 7 hr, and of the slow phase, 42 hr. The ratio of the radioactivity found in the rough to the radioactivity found in the smooth endoplasmic reticulum was 0.70 while the ratio of the CO-binding pigment found in each subfraction was 0.68, further strenghtening the concept that the radioactivity found in the CO-binding particles is incorporated exclusively into CO-binding hemoprotein.