L-Arginine:glycine amidinotransferase (trans-amidinase) occurs at high concentrations in the kidney and the pancreas of rats. The cellular localization of transamidinase was investigated in fetal, neonatal, and adult rat pancreatic tissue using three indicators of the presence of transamidinase: (1) immunofluorescence microscopy, (2) in vitro enzymatic activity measurements on homogenates of whole pancreas and on isolated acinar and islet tissue from adult rats, and (3) ornithine production from perfused adult rat pancreas. The cellular local-ization of transamidinase was determined in fetal, neonatal, and adult rat pancreas, using a polyclonal guinea pig antibody made against a highly purified preparation of kidney transamidinase. Immunoreactive transamidinase was detected only in the pancreatic acinar cells. The cellular distribution of the immunostaining was compatible with the presence of transamidinase in mitochondria. The transamidinase enzymatic activity of whole pancreatic homogenates was 13.4 ± 0.7 U/g wet weight in = 11). Inpancreata where islets had been isolated away from the acinar tissue, the transamidinase activity was similar to that of the whole pancreatic homogenates (16.8 ± 2 U/g wet weight). Any transamidinase activity present in isolated islets was below the sensitivity of the assay. Transamidinase activity in the isolated perfused pancreas was determined by measuring the amount of ornithine released into the perfusate. The transamidinase activity of the perfused pancreas was 16.4 ±1.8 U/g pancreas and is an estimate of the physiological production capacity of the enzyme (270 ± 29 nmol ornithine/min/g pancreas). These results indicate that transamidinase is present at high concentrations in the pancreas. Within the pancreas, the enzyme was present only in acinar cells of fetal, neonatal, and adult rats. Transamidination products that may be provided to the liver by way of the portal vein are largely, if not exclusively, derived from the pancreatic acinar cells.
- Acinar cells
- Guani-dinoacetic acid
- L-Arginine:glycine amidinotransferase