Somatostatin-like peptides alter calcium but not secretin sensitivity of gastrinoma cells.

The provocation of gastrin release by calcium or secretin is accepted as a method to differentiate the hypergastrinemia of the Zollinger-Ellison syndrome from that of other causes. We have previously shown that calcium and secretin failed to provoke gastrin release from acutely dispersed gastrinoma cells. This disparity between the in vivo and in vitro effects of these two provocative agents suggests that intermediates may be necessary for calcium- or secretin-induced gastrin release. In an acute cell dispersion, serum-free model, two gastrinomas with low levels of endogenous somatostatin (SRIF) and other peptides failed to respond to calcium or secretin provocation. Conversely, a third tumor containing high levels of endogenous SRIF-like peptides and low levels of other gut peptides did respond to calcium, but not to secretin provocation in vitro. We suggest that in vivo, SRIF modulation of gastrin release is a prerequisite for calcium-simulated gastrin secretion.