Fig. 2. Characterization of secretion stimulated by different doses of carbachol. Parotid lobules were pulse labeled and chased for 180 minutes before stimulation and, at each timepoint, the medium was completely removed and replaced. (A) Time course of secretion of amylase enzyme upon stimulation with 40 nM CCh, 200 nM CCh and 2 µM CCh. (B) Specific radioactivity of amylase was calculated as in Fig. 1. (C) Left panel, radiochemical composition of secretion elicited by 2 µM CCh after 1 minute of stimulation. Right panel, coomassie-stained profiles for samples of secretion collected following stimulation with 40 nM (lanes 1,2) and 2 µM (lanes 3,4) CCh. Lanes 1 and 3 show profiles for the first 3 minutes of stimulation, lanes 2 and 4 show profiles from the 10-15 minute interval. For comparison, lane 5 shows a sample collected after 15 minutes of stimulation with 1 µM Iso. Data are from one of three experiments with the same outcome.