Effect of somatostatin on rabbit isolated coronary arteries

The role of somatostatin and its receptors (sstr2, sstr5) in the contractility of gilt inflamed uterus

We studied the inflammation effect on somatostatin receptors subtypes 2 (sstr2) and 5 (sstr5) expression in myometrium and somatostatin influence alone or with sstr2 and sstr5 antagonists on the contractility of gilt inflamed uterus. On day 3 of the estrous cycle, either E.coli suspension (E.coli group) or saline (SAL group) were injected into uterine horns. In the control pigs (CON group), only laparotomy was performed. Eight days later, in the E.coli group developed severe acute endometritis. In this group, myometrial sstr2 mRNA expression lowered and protein expression increased compared to other groups. Compared to period before somatostatin administration, somatostatin did not change tension in myometrium and endometrium/myometrium of three groups, reduced amplitude and frequency in the CON and SAL groups, and increased amplitude and decreased frequency in the E.coli group. In this group, amplitude was increased by somatostatin compared to other groups. In the CON and SAL groups, sstr2 eliminated inhibitory somatostatin effect on amplitude, while sstr5 antagonist reversed inhibitory somatostatin effect on amplitude. In the E.coli group, sstr2 antagonist reversed stimulatory somatostatin effect on amplitude, while in sstr5 antagonist presence stimulatory somatostatin effect was more deepened compared to somatostatin action alone. After using sstr2 antagonist more deepened inhibitory somatostatin effect on frequency in the CON and E.coli groups was found. Sstr5 antagonist partly eliminated inhibitory somatostatin effect on frequency in the SAL group. Summarizing, the uterine inflammation increases the myometrial sstr2 protein expression; somatostatin raises amplitude of the inflamed uterus acting by sstr2, while drops this parameter by sstr5.

Inhibitory effects of somatostatin on cholecystokinin octapeptide induced bile regurgitation under stress: ionic and molecular mechanisms

OBJECTIVE

To investigate the possible effects and related ionic and molecular mechanisms of changes of plasma cholecystokinin octapeptide and somatostatin on stress-induced bile regurgitation in rats.

METHODS

In forty healthy adult rats, changes of plasma cholecystokinin octapeptide, somatostatin and intragastric bile concentration under stressful condition were respectively measured by specific radioimmunoassay methods. Contractile responses of gastric antral smooth strips isolated from healthy adult rats were recorded by polyphysiograph. Immunoprecipitation was used to determine the regulatory effect of protein kinase C on regulating the phosphorylation of type 3 inositol 1,4,5-triphosphate receptor (InsP3R3) in gastric smooth muscle cells. Changes of intracellular calcium fluorescence intensity of smooth muscle cells presented as intracellular calcium ([Ca2+]i) were analyzed under laser scanning confocal microscopy and L-type voltage-dependent calcium currents of smooth muscle cells were recorded by patch-clamp techniques.

RESULTS

Compared with the normal control group, plasma cholecystokinin octapeptide and gastric bile concentration of each stress group significantly increased during the stress, while adverse effect was obtained in plasma somatostatin, which decreased from the beginning of the stress and attained the minimum nearly at the same time when the plasma cholecystokinin octapeptide concentration reached the maximum. Respective addition of cholecystokinin octapeptide and somatostatin with increasing concentrations caused rapid, sustained, concentration-dependent increase and decrease in muscle contraction of gastric antral strips, and cholecystokinin octapeptide that increased the contractile response could be blocked by respective administration of nifedipine and somatostatin significantly. Similar results were obtained in the changes of calcium fluorescence intensity and calcium currents of smooth muscle cells. Pretreatment with somatostatin significantly increased cholecystokinin octapeptide-increased phosphorylation of InsP3R3 in smooth muscle cells.

CONCLUSIONS

Gastric mucosal damage induced by bile regurgitation is closely connected with gastric antral dysmotility evoked by the changes of cholecystokinin octapeptide and somatostatin under stressful condition. Cholecystokinin octapeptide-intensified contraction depends on the release of intracellular calcium stores and the influx of extracellular calcium via L-type voltage-dependent calcium channels, while this excitatory effect of cholecystokinin octapeptide could be blocked by somatostatin, suggesting that both of the two peptides play important roles in the regulation of gastric motility.

Somatostatin induces rapid contraction of neuroendocrine cells

The peptide hormone somatostatin, as well as the somatostatin analog octreotide, induces rapid morphological changes in neuroendocrine cells. The effect can be detected in less than 2 min: retraction fibers are formed, cells round up and cell-cell contacts are broken. Somatostatin-dependent cell contraction is inhibited by Y-27632, indicating that this effect is dependent on Rho kinase. In BON1 cells, the somatostatin-induced inhibition of forskolin-induced secretion of chromogranin A is not blocked by Y-27632. It is therefore concluded that the inhibitory effect of somatostatin in forskolin-stimulated cells is not dependent on cell contraction.