J. Tamaoki et al., ATYPICAL ADRENOCEPTOR-MEDIATED RELAXATION OF CANINE PULMONARY-ARTERY THROUGH A CAMP-DEPENDENT PATHWAY, Biochemical and biophysical research communications (Print), 248(3), 1998, pp. 722-727
We studied the existence of beta(3)-adrenoceptors in canine pulmonary
artery smooth muscle under isometric conditions in vitro. A rank order
potency of vascular relaxation was isoproterenol > salbutamol > selec
tive beta(3)-adrenoceptor agonists, CL 316243 and BRL 37344, A marked
desensitization to salbutamol occurred by pretreatment with salbutamol
but not with CL 316243, When beta(1)-adrenoceptors were blocked, the
relaxant responses to salbutamol were competitively antagonized by the
beta(2)-adrenoceptor antagonist ICI 118551, whereas the response to C
L 316243 was not. Cyanopindolol, a non-selective beta-adrenoceptor ant
agonist, antagonized CL 316243-induced relaxation in a competitive man
ner with a pA(2) of 6.10, and this value was lower than that when salb
utamol was used as an agonist (6.69), Intracellular cAMP levels were i
ncreased by CL 316243, an effect that was not altered by ICI 118551, T
herefore, beta(3)-adrenoceptors may be present and functioning in cani
ne pulmonary artery. (C) 1998 Academic Press.