The molecular form distribution of adenosine deaminase has been characterized in nine rat tissues. This study has also investigated the effects of 70% partial hepatectomy in liver, spleen, and intestinal tissues. In all tissues studied, the molecular weight of the enzyme was found to be 35,000 daltons, as determined by gel filtration chromatography. Two prominent isozymes of this molecular weight were identified by means of thin-layer isoelectric focusing. Isozymes with pI's of 4.95 and 4.80 were present in tissues of liver, spleen, and intestine of normal and hepatectomised rats. Throughout the liver regeneration period, activity levels of adenosine deaminase were elevated in all tissues examined.Ball State UniversityMuncie, IN 47306