Biologic half-life and organ distribution of radiolabeled human PiM and PiZ alpha-1-antitrypsin in the dog.

Highly purified A-1-A.T., prepared from blood obtained from donors of known PiZZ and PiMM phenotype, was radiolabeled with 125I or 131I and injected intravenously into dogs. The radiolabeled proteins retained their prelabel electrophoretic and trypsin-inhibitory characteristics. The biologic t1/2 of both M and Z protein in the circulation were similar, averaging 71 hr for M protein and 80 hr for Z protein. The label was shown to remain tightly bound in vivo for 2 days after injection. The material was nonpyrogenic in rabbit and dog. No arteriovenous differences in radioactivity could be detected at 2 or 20 min after injection. However, surface scanning disclosed substantial pulmonary deposition of radioactivity for the first 9 hr after injection. At 48 hr, intense radioactivity was present in the spleen, but not in the liver. These studies indicate the feasibility of similar studies in man, including noninvasive assessment of body distribution of M and Z protein by surface scanning techniques.