3H-methyl scopolamine binding to dispersed pancreatic acini

Maximal amylase release occurred with 10(-5) M carbachol and slightly greater than half maximal response occurred with 3 x 10(-7) M carbachol in dispersed pancreatic acini. The preparation released more than 45% of its initial amylase content after 60 min of maximal carbachol stimulation. Electron microscopy revealed depletion of zymogen granules and the presence of secretory material in the ductules after carbachol stimulation. At 37 degrees C, maximal binding of methyl scopolamine occurred in about 45 min with 3 x 10(-10) M 3H-methyl scopolamine. The dissociation constant for 3H-methylscopolamine was 6.8 x 10(-10) M and saturation occurred at 109 pm/g protein. The I.C. 50 for 3H-methylscopolamine inhibition of carbachol-induced amylase secretion was 7 x 10(-10) M.