| Abstract: | The studies deal with the influence of secretin and various ecbolic secretagogues on tissue levels of cAMP and cGMP in vivo and in the isolated perfused canine pancreas. The mutual behaviour of cellular cAMP and cGMP is observed and compared with the time course of the respective secretory events. Synthetic secretin as well as CCK, acetylcholine or Caerulein likewise elevate tissue cAMP and cGMP simultaneously. There exists no difference in the magnitude of increase and in the time course of changes in tissue cyclic nucleotide levels between hydrokinetic and ecbolic stimulation. The rise in cAMP and cGMP coincides with the onset of the respective secretory events and reaches peak values contemporarily to the excretory maxima. The following decrease in tissue cyclic nucleotides approximatively parallels juice or enzyme secretion in the isolated perfused pancreas but differs widely in vivo. Under this condition cAMP and cGMP rapidly fall to basal levels during undiminished excretory function and show a second rise after cessation of the latter. Secretin and various ecbolic secretagogues do not increase tissue content of cyclic nucleotides in the same dose-dependent manner as can be observed with pancreatic secretion. The behaviour of cAMP and cGMP after addition of secretin and CCK or acetylcholine remains widely unchanged during calcium-free perfusion in spite of an extensive excretory inhibition. The corresponding rise in cellular cAMP and cGMP in the sequence of hydrokinetic as well as of ecbolic stimulation points to an analogous intracellular mediation of various secretagogues in different target cells of the exocrine canine pancreas. |
