AJP - Gastrointestinal and Liver Physiology, Vol 241, Issue 1 67-G73, Copyright © 1981 by American Physiological Society
Digestive end products mobilize secretory proteins from subcellular stores in the pancreas
J. H. Grendell and S. S. Rothman
Two digestive end products, D-glucose and L-lysine, produced substantial
concentration-dependent release of amylase and trypsinogen, respectively,
from subcellular storage pools into a postmicrosomal supernatant fraction
of rat pancreatic tissue homogenate. This process was selective in that
D-glucose did not lead to trypsinogen release, while L-lysine did not
effect amylase. An analogue of D-glucose, 2-deoxy-D-glucose, was much less
potent than D-glucose on an equimolar basis. Half-maximal release for both
end-product enzyme pairs occurred at concentrations within the range of
normal plasma values for these end products in the rat. Although amylase
release reached an apparent plateau when the concentration of glucose was
increased beyond the maximally effective level, lysine concentrations
higher than that maximally effective resulted in a fall in trypsinogen
release that ultimately returned (at 3.0 mM L-lysine) to the level seen in
its absence. When isolated zymogen granules were exposed to the same
concentrations of D-glucose or L-lysine, a similar pattern of release was
seen, indicating that the zymogen granules are a source of the enzymes
released from the particulate phase of the homogenates. These findings can
be explained most simply by the selective movement of digestive enzymes
across zymogen granule membranes in response to the presence of appropriate
end products. They are also consistent with the concept that digestive end
products can act rapidly and directly on the pancreatic acinar cell to
regulate the mixture of enzymes secreted in response to the specific
hydrolytic needs of a meal.
