F. Sugimoto et al., EFFECT OF SOMATOSTATIN ON CONTRACTILE AND RELAXANT RESPONSES OF TRACHEAL SMOOTH-MUSCLE IN RABBITS, Research communications in chemical pathology and pharmacology, 80(3), 1993, pp. 295-304
To determine the effect of somatostatin (SRIF) on airway smooth muscle
contractile and relaxant responses and its mechanism of action, we st
udied rabbit tracheal smooth muscle under isometric conditions in vitr
o. SRIF did not change the contractile responses to electrical field s
timulation and acetylcholine, but it inhibited the relaxant responses
to isoproterenol in a concentration-dependent manner, an effect that w
as reversed by treatment of tissues with pertussis toxin (PTX). In con
trast, the forskolin- and verapamil-induced relaxations were not alter
ed by SRIF. SRIF also attenuated the increase in intracellular cyclic
AMP levels in response to isoproterenol. These results suggest that SR
IF may decrease beta-adrenoceptor-mediated muscle relaxation by acting
at the site proximal to cyclic AMP synthesis, especially at PTX-sensi
tive GTP-binding regulatory protein, G(i), coupled to adenylate cyclas
e.