Frequency-dependent secretion of pancreatic amylase, lipase, trypsin, and chymotrypsin during vagal stimulation in rats

Abstract

Pancreatic enzyme secretion in rats has been shown to be stimulated differentially by the intestinal hormones secretin and cholecystokinin. Since it is unknown if activation of neural mechanisms have similar effects, it was the aim of the present study to examine in anesthetized rats the output of the pancreatic enzymes amylase, lipase, trypsin, and chymotrypsin before (15 min), during, and after (30 min each) vagal stimulation (5 ms, 10 V) with different frequencies (0.5, 5, 10, and 50 Hz). At 5 Hz, a maximal stimulation of all four enzymes was observed, with a peak towards the end of the vagal stimulation period. At 0.5 Hz, amylase, trypsin, and chymotrypsin were released not only in smaller quantities but also in a different time pattern (trypsin and chymotrypsin), with a maximum early during vagal stimulation. Lipase secretion remained unchanged at 0.5 Hz. At 10 Hz, the output of amylase, lipase, and trypsin was quantitatively less compared to 5 Hz. In contrast to stimulation at 0.5 and 5 Hz, the maximal enzyme output was reached after cessation of vagal stimulation (amylase and lipase). Chymotrypsin release did not change in response to vagal stimulation at 10 Hz. A frequency of 50 Hz had no influence on the secretion of any of the four enzymes determined. These data demonstrate that activation of the vagus nerves can lead to a differential release of pancreatic enzymes. The exact regulatory mechanisms of action are as yet unknown and remain to be determined.