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Potential mediation of somatostatin secretion from canine fundic D-cells by protein kinase c
Abstract:
We examined the possible importance of protein kinase c-dependent mechanisms in mediating the stimulatory effects of gastrin and cholecystokinin (CCK) on the release of somatostatin-like immunoreactivity (SLI) from isolated canine fundic D-cells. Diacylglycerides, presumably the products of phosphoinositide breakdown that activate protein kinase c, and phospholipase C, which catalyzes the production of endogenous diacylglycerides from membrane phospholipids, both stimulated SLI secretion in a dose-dependent fashion. Both classes of agents potentiated the actions of adenosine 3',5'-cyclic monophosphate-dependent agonists but not those of gastrin and CCK. The stimulatory effects of gastrin and CCK correlated with their abilities to enhance the incorporation of 32P into membrane phosphatidyl inositol and phosphatidic acid and promote the release of [3H]inositol trisphosphate from prelabeled D-cells, two parameters of phosphoinositide turnover. These data suggest that protein kinase c may serve to transduce the signals activated by gastrin and CCK in D-cells.
Insights
Protein kinase C pathways are crucial for regulating somatostatin-like immunoreactivity (SLI) release stimulated by gastrin and cholecystokinin (CCK). These findings highlight a key signaling mechanism in canine fundic D-cells.
Area of Science:
- Cellular signaling
- Gastrointestinal endocrinology
- Molecular biology
Background:
- Gastrin and cholecystokinin (CCK) stimulate somatostatin-like immunoreactivity (SLI) release from canine fundic D-cells.
- The precise intracellular mechanisms mediating these hormonal effects are not fully understood.
Purpose of the Study:
- To investigate the role of protein kinase C (PKC)-dependent pathways in gastrin and CCK-stimulated SLI release.
- To elucidate the involvement of phosphoinositide turnover in this signaling cascade.
Main Methods:
- Isolated canine fundic D-cells were used to assess SLI secretion.
- Experiments involved stimulating cells with diacylglycerides, phospholipase C, gastrin, and CCK.
- Phosphoinositide turnover was measured by monitoring 32P incorporation into phospholipids and [3H]inositol trisphosphate release.
Main Results:
- Diacylglycerides and phospholipase C dose-dependently stimulated SLI secretion.
- Gastrin and CCK enhanced phosphoinositide turnover, indicated by increased 32P incorporation and [3H]inositol trisphosphate release.
- PKC activation potentiated cyclic AMP-dependent agonists but not gastrin or CCK directly.
Conclusions:
- Protein kinase C activation is implicated in transducing signals from gastrin and CCK in D-cells.
- These findings suggest a novel signaling pathway involving phosphoinositide turnover and PKC in regulating SLI release.