Resumo

GUEVARA DE MURILLO, A; DE VILLARROEL, SS; DE BECEMBERG, Lippo  e  ALFONZO, M. Efecto de la Toxina Pertussis sobre la actividad Guanilil Ciclasa Dependiente de Mg²⁺ en el Músculo Liso Traqueal de Bovino. RFM [online]. 2002, vol.25, n.1, pp.70-72. ISSN 0798-0469.

Plasma membranes from bovine tracheal smooth muscle show a Mg²⁺ dependent guanylyl cyclase activity, which was assayed using radioimmunoassay for cGMP and the effect of pertussis toxin on this cyclase activity was studied. Such enzymatic activity was dependent of Mg²⁺ concentration and reached a maximal activity at Mg²⁺ 2 mM,at higher Mg²⁺ concentration showed an inhibitory effect. The agonist carbamylcholine had a dual effect: stimulatory until 10^-9 M and inhibitory at higher concentration level. The pertussis toxin produces a blocking effect on Mg²⁺ dependent guanylyl cyclase, this fact permits to conclude that this enzymatic activity is modulated by a G protein Go/Gi in similar manner as guanylyl cyclase-Mn²⁺ but apparently for guanylyl cyclase-Mg²⁺ is required the presence of the inhibitor component of G protein.

Palavras-chave : Guanylyl cyclase-Mg²⁺; Tracheal smooth muscle; Pertussis toxin; Go/Gi proteins.