The effect of various cholinergic drugs on incorporation of 3H-leucine into protein of rat pancreas in vitro was studied. It was found that carbachol and bethanechol, but not pilocarpine, inhibited incorporation 70–80%. Even in the continued presence of carbachol, the rate of incorporation is depressed only 40–60 min. It recovers and eventually exceeds that seen in untreated tissue. After 4 h incubation the amount of 3H-leucine incorporated into protein is the same in carbachol-treated and untreated tissue. The alteration of amino acid incorporation can be dissociated from the effect of the drug on secretion in several ways: (1) calcium deprivation abolishes carbachol-stimulated secretion but not the inhibition of amino acid incorporation; (2) atropine, 10−8 M, totally abolishes the effect of carbachol on amino acid incorporation without affecting secretion (10−5 M atropine is needed to abolish carbachol stimulated secretion); (3) pilocarpine stimulates secretion but has no effect on amino acid incorporation. The inhibition of amino acid incorporation is not due to inhibition of amino acid transport nor to a decrease in tissue ATP concentration. It is concluded that there is no clear relationship between protein secretion and synthesis. Muscarinic agents, which stimulate secretion of protein, may also cause changes in the rate of amino acid incorporation into protein; however, the change one measures will depend on when, after administration of the secretagogue, protein synthesis is measured.
