Secretion of new digestive enzyme by pancreas with minimal transit time

A small amount of labeled digestive enzyme is secreted within 5 min of adding radioactive leucine to whole rabbit pancreas in vitro. This rapid secretion of labeled protein suggests that some new protein is able to bypass intracellular storage pools and is secreted immediately. The amount of protein secreted this way varies inversely with overall protein secretion in the unstimulated state and is decreased as the result of cholinergic stimulation of protein secretion as well. Under the conditions studied, a mean of 2.5% of secreted protein is apparently not stored prior to secretion.