Actions of somatostatins on gastric smooth muscle cells.
The effects of somatostatin-28, somatostatin-14, and a synthetic somatostatin octapeptide analogue, D-Phe-Cys-Tyr-D-Trp-Lys-Thr-Cys-Nal-NH2 (cyclo SS-8) were examined on contraction of dispersed gastric smooth muscle cells from guinea pigs. The somatostatins did not cause contraction of gastric smooth muscle cells, nor did they inhibit carbachol-stimulated contraction. However, they reversed vasoactive intestinal peptide (VIP)-induced inhibition (relaxation) of carbachol-stimulated contraction. Somatostatin-28 had a half-maximal effect (EC50) at 1.6 +/- 0.8 nM, cyclo SS-8 at 0.6 +/- 0.3 nM, but somatostatin-14 had no effect even when used in concentrations as high as 1 microM. Incubation of muscle cells with peptidase inhibitors phosphoramidon (1 microM) plus amastatin (10 microM) had no effect on the EC50 of somatostatin-28 or cyclo SS-8 but increased the potency of somatostatin-14 greater than 1,000-fold. When peptides were incubated with muscle cells and the products applied to high-performance liquid chromatography, cyclo SS-8 was not degraded, but somatostatin-14 was rapidly degraded when present alone, and the addition of peptidase inhibitors partially inhibited the degradation. Cyclo SS-8 had its maximal effect at 0.5-1 min and inhibited relaxation induced by VIP, isoproterenol, glucagon, or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). Cyclo SS-8 partially inhibited the increase in VIP-stimulated cAMP. Preincubation with pertussis toxin blocked the inhibitory action of cyclo SS-8 on VIP or DBcAMP-induced relaxation. These results indicate that gastric smooth muscle cells rapidly degrade somatostatin-14 and suggest that muscle cell peptidases could have a major effect on the actions of somatostatin-14.(ABSTRACT TRUNCATED AT 250 WORDS)
Gu
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ZF
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Pradhan
T
T
Coy
D H
DH
Mantey
S
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Bunnett
N W
NW
Jensen
R T
RT
Maton
P N
PN
D000595:Amino Acid Sequence; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005934:Glucagon / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000494:pharmacology; D011498:Protein Precursors / Q000502:physiology; D013004:Somatostatin / Q000031:analogs & derivatives / Q000502:physiology*; D053561:Somatostatin-28; D013270:Stomach / Q000187:drug effects / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D011498:Protein Precursors; C073699:phenylalanyl-cysteinyl-tyrosyl-tryptophyl-lysyl-threonyl-cysteinyl-N-naphthylalanine amide; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D003994:Bucladesine; D053561:Somatostatin-28; D002217:Carbachol; D005934:Glucagon; D000242:Cyclic AMP; D007545:Isoproterenol; D015282:Octreotide