RT Journal Article
SR Electronic
T1 Functional assessment of β adrenoceptor subtypes in human colonic circular and longitudinal (taenia coli) smooth muscle
JF Gut
JO Gut
FD BMJ Publishing Group Ltd and British Society of Gastroenterology
SP 337
OP 342
DO 10.1136/gut.47.3.337
VO 47
IS 3
A1 L Manara
A1 T Croci
A1 G Aureggi
A1 F Guagnini
A1 J-P Maffrand
A1 G Le Fur
A1 S Mukenge
A1 G Ferla
YR 2000
UL http://gut.bmj.com/content/47/3/337.abstract
AB BACKGROUND AND AIMS The subtype and species related heterogeneity of β adrenoceptors prompted a functional reappraisal of these molecular targets of motility inhibition in the human colon.METHODS Relaxation of muscle strips was measured in vitro.RESULTS The following agonists had decreasing relaxing potency (effective concentration range 10−8–10−4 mol/l): (−)isoprenaline (non-selective), terbutaline (β2 selective), CGP 12177 (β3 selective, also β1, β2antagonist), and SR 58611A (β3 selective). Isoprenaline and terbutaline were more potent on circular than taenia strips; CGP 12177 and SR 58611A weakly and partially relaxed taenia but had little effect on circular strips. The potency of isoprenaline on circular strips was greatly reduced by the β1 selective antagonist CGP 20712 (10−7 mol/l), and less so by ICI 118551 (10−7 mol/l, β2 selective). CGP 20712 and ICI 118551 together (both 3×10-6 mol/l) had no effect on taenia relaxation by SR 58611A and rendered isoprenaline and terbutaline virtually inactive on circular strips, although not on taenia, which was relaxed at higher than control concentrations and maximally by isoprenaline. Propranolol, a β1, β2 non-selective antagonist, at high concentrations (10-5 mol/l) prevented taenia relaxation by CGP 12177 and SR 58611A; its quantitative antagonism of isoprenaline (in common with that of CGP 12177 used as an antagonist) was competitive in circular strips but not on taenia.CONCLUSIONS β1, β2, and β3 adrenoceptors are functionally detectable in the human colon; agonist stimulation of any one type relaxed taenia but only isoprenaline was fully effective at the β3 subtype.IC50concentration producing 50% maximal response