Korean J Physiol Pharmacol.  1999 Jun;3(3):275-282.

Involvement of Spontaneously Formed Cyclic Nucleotides in Cat Gastric Muscle Relaxation

• Sim SS
• Baek HJ
• Rhie DJ
• Yoon SH
• Hahn SJ
• Jo YH
• Kim MS

Abstract

Muscle strips and muscle cells from cat stomach were used to investigate whether spontaneously formed cyclic nucleotides were involved in the inhibition of gastric smooth muscle contraction. A phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), increased the levels of both cyclic GMP (cGMP) and cyclic AMP (cAMP) in resting state cells, while decreasing acetylcholine-induced muscle contraction. Under the influence of IBMX, SQ22536, an adenylyl cyclase inhibitor and methylene blue, a guanylyl cyclase inhibitor completely blocked increases in cAMP and cGMP respectively, without any effect on contraction. However, the combination of SQ22536 and methylene blue completely blocked increases in both cAMP and cGMP levels and stimulated contractions markedly even in the presence of IBMX. Muscle contraction inhibitors such as isoprenaline, vasoactive intestinal polypeptide and sodium nitroprusside also appeared to increase cyclic nucleotide levels which decreased contraction. Which nucleotide increased the most was dependent on the agonist used. Therefore, irrespective of the cyclic nucleotide class, the spontaneous formation of cyclic nucleotides should be considered in evaluating the mechanism of gastric smooth muscle relaxation.

Keyword

Smooth muscle relaxation; Cyclic AMP; Cyclic GMP; Cat stomach

MeSH Terms

1-Methyl-3-isobutylxanthine
Adenylyl Cyclases
Animals
Cats*
Cyclic AMP
Cyclic GMP
Guanylate Cyclase
Isoproterenol
Methylene Blue
Muscle Cells
Muscle Contraction
Muscle Relaxation*
Muscle, Smooth
Nitroprusside
Nucleotides, Cyclic*
Relaxation
Stomach
Vasoactive Intestinal Peptide
1-Methyl-3-isobutylxanthine
Cyclic AMP
Cyclic GMP
Guanylate Cyclase
Isoproterenol
Methylene Blue
Nitroprusside
Nucleotides, Cyclic
Vasoactive Intestinal Peptide