Resumen

HASSAN-SOTO, Walid et al. Selective Mastoparan inhibition of muscarinic activation of bovine tracheal smooth muscle. AVFT [online]. 2012, vol.31, n.4, pp.72-79. ISSN 0798-0264.

Muscarinic activation of bovine tracheal smooth muscle (BTSM) leading to smooth muscle contraction involves the generation of two cGMP signals (20 and 60 s), being 20s peak associated with soluble (sGC) and the second (60s) to membrane-bound Natriuretic Peptide- receptor-Guanylylcyclases (NPR-GC). In this study, we showed that pre-incubation of isolated BTSM strips with mastoparan and superactive mastoparan (mastoparan 7) decreased significantly the muscarinic dependent contractile smooth muscle responses in dose-dependent and non-competitive manner. Moreover, mastoparan (50 nM) inhibited completely the BTSM-muscarinic contractile responses and affected dramatically the carbachol-dependent cGMP signals being the first cGMP signal inhibited in a 63 ± 5%, whereas the second signal disappeared. Mastoparan inhibition of muscarinic activation is specific since other spasmogens as serotonin and histamine fully contracted these BTSM strips under mastoparan treatment. Cyclic GMP levels were evaluated by exposing BTSM strips to activators of NO-sensitive sGC as Sodium Nitroprussiate (SNP) and Natriuretic Peptides as CNP-53 for membrane-bound NPR-GC. Thus, SNP and CNP increased in a binary way, in more than 20 fold cGMP levels at 30-40 s being both increments inhibited by mastoparan. Furthermore, the Gi/o-protein involvement on mastoparan inhibition of cGMP elevations induced by CNP and SNP is suggested by Pertussis toxin pre-treatment, which reversed mastoparan effects. These results indicate that muscarinic signal transduction cascades leading to airway smooth muscle contractions involved two different guanylyl cyclases being both regulated by mastoparan-sensitive G-proteins. Abbreviations: ANP, Natriuretic Peptide type A; ASM, Airway Smooth Muscle; BTSM, Bovine Tracheal Smooth Muscle; CNP-53, Natriuretic Peptide type C-53; GPCR, G-Protein Coupled Receptor; Gq16, Heterotrimeric G protein subtype 16; Gi/o, Heterotrimeric G protein subtype i/o; m2AChR, muscarinic receptor type 2; m3AchR, muscarinic receptor type 3; NP, Natriuretic Peptides; NPR-GC, Natriuretic Peptides Receptor Guanylyl Cyclase; NPR-A, Natriuretic Peptides Receptor Guanylyl Cyclase type A ; NPR-B, Natriuretic Peptides Receptor Guanylyl Cyclase type B; PTX, Pertussis Toxin; sGC, soluble Guanylyl Cyclase; SNP, sodium nitroprusside; ODQ, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; PDE, cyclic nucleotide phosphosdi-esterase; TCA, tricloroacetic acid and BTSM, Bovine tracheal smooth muscle.

Palabras clave : Tracheal smooth muscle; carbachol; mastoparan; soluble guanylyl cyclase; Natriuretic Peptide Receptor-guanylyl cyclase.