Studies on dispersed pancreatic exocrine cells. II. Functional characteristics of separated cells

The functional characteristics of separated guinea pig pancreatic exocrine cells have been examined following dissociation of the gland by a procedure described in the previous paper (J. Cell Biol. 1974. 63:1037). The ability of isolated cells to incorporate labeled amino acids into secretory proteins was assessed biochemically and by quantitative electron microscope autoradiography. Incorporation remained linear for up to 4-h incubation at levels equivalent to those of pancreatic slices; over 95% of the exocrine cells in the population were viable, and all appeared to be equally active in incorporating amino acids. The capacity of separated cells to transport, concentrate, and store exportable proteins was monitored by electron microscope autoradiography on populations pulse labeled with [(3)H]leucine and chase incubated for 4 h. The same overall pathway previously mapped in pancreatic slices was followed by secretory proteins in separated cells although in quantitative studies a defect was noted in the rate of conversion of condensing vacuoles to zymogen granules. Secretogogue responsiveness was assessed by monitoring discharge of labeled secretory proteins or of amylase in response to carbamylcholine and caerulein to the medium. While the separated cells released secretory proteins linearly for up to 4 h in response to both secretogogues, the net release was approximately 50% less than previously noted for pancreatic slices and required a ten times higher concentration of stimulant. The defect may represent alteration in receptors due to the protease used for dissociation. Our data indicate, however, that separated exocrine cells retain their ability to process secretory proteins stepwise and vectorially which is consistent with preservation of structural polarity.