SOMATOSTATIN BINDING-CAPACITY, GUANYLATE-CYCLASE AND TYROSINE PHOSPHATASE-ACTIVITIES DURING PANCREATIC PROLIFERATION IN THE RAT INDUCED BY GASTRECTOMY

Gastrectomy increased pancreatic growth and this effect was associated with an increase in the number of somatostatin-14 (SS) receptors (146 % of control) without altering their affinity. SS increased guanylate cyclase activity twofold in pancreatic acinar membranes from gastrecto mized rats. The gastrectomy decreased pancreatic SS-like immunoreactiv ity (SS-LI) content (55% of control levels) and tyrosine phosphatase a ctivity (74% of control levels). Administration of proglumide (20 mg/k g, IF), a gastrin/cholecystokinin (CCK) receptor antagonist, suppresse d the inhibitory effect of gastrectomy on basal tyrosine phosphatase a ctivity and SS-LI content, which returned to control levels. Furthermo re, proglumide suppressed the increase of the number of SS receptors a nd of SS-stimulated guanylate cyclase activity induced by gastrectomy. All this suggests that pancreatic acinar cell growth is associated wi th upregulation of SS receptors, which could represent a mechanism pro moted by the cell to negatively regulate the mitogenic activity of pan creatic growth factors such as CCK. In addition, the results also sugg est that the negative regulation of tyrosine phosphatase activity may be important in the events involved in the pancreatic hyperplasia obse rved after gastrectomy.