Autoradiographic observations on the incorporation of amino acids into oesophageal, gastric and pancreatic glands in the leopard frog, Rana pipiens.

The uptake and incorporation of L-3H-leucine and L-3H-serine in the oesophageal, gastric and pancreatic exocrine glands of Rana pipiens was examined using light microscopic autoradiographic techniques. At 1/2 h, 1 1/2 h and 3 h following injections of amino acids, silver grains are observed over the basal region of the cells comprising the glands. At 6 h after injection, silver grains occur over the apical region of the cells and by 24 h the grains can be observed over the cytoplasm of the cells adjacent to the lumen of the glands, collecting ducts, oesophagus and stomach. These observations indicate that the amino acids are being incorporated into proteins that are then discharged into the lumen of the pancreatic ducts, oesophagus and stomach. The secretory picture observed in the oesophageal glands closely resembles that of the gastric glands. This autoradiographic study supports the suggestion that the two glands are homologous and that they both secrete pepsinogen granules.