Binding characteristics of (+)-, (�)- and (-)-[125Iodo] cyanopindolol to guinea-pig left ventricle membranes

The affinity and efficacy of the selective β1‐adrenoceptor stimulant RO363 at β1‐ and β2‐adrenoceptor sites

“…The results of the kinetic studies indicate a similar association rate to that previously found for the ligand (Hoyer et al, 1982) (Brodde etal., 1981;Engel et al, 1981Hoyer et al, 1982 which presumably arises from two different affinity states of the receptor (Hoyer et al, 1982). One possible explanation for the different number of phases in dissociation studies is that a complete ionic buffer was used in the present study, whereas previous workers used isotonic saline buffered with 10 mM Tris-HCl.…”

“…The rate of association of [1251]-CYP to atrial and uterine membranes was determined at 0, 6, 10, 20, 50 and 120 min. The association rate constant (k,) was calculated as described by Hoyer et al, (1982). Dissociation was determined at 0, 2, 4,6,8,10,30,50,70,90,120,150,180,210 and 240 min after the addition of 1 giM propranolol.…”

Interaction of the antiarrhythmic agents SR 33589 and amiodarone with the β‐adrenoceptor and adenylate cyclase in rat heart

“…Figure 4 illustrates the rate of dissociation of ['25"1-(-)-CYP from the fadrenoceptor at equilibrium in the absence and presence of SR 33589 or amiodarone. As described previously (Hoyer et al, 1982), the dissociation of ["-2I]-(-)-CYP was biphasic with a slow component (k-1 3.70±0.34x l0-3 min'-representing e70% of the total number of binding sites, n=4) and a fast SR 33589 (1-500 tM) and amiodarone (1-500 tiM) alone or in the presence of 10 pM GTP did not increase the corresponding adenylate cyclase activity. The activity of adenylate cyclase was inhibited in a dose-dependent manner by SR 33589 ( Figure 5) and amiodarone (data not shown).…”

Hypoxia and glucose independently regulate the beta-adrenergic receptor-adenylate cyclase system in cardiac myocytes.

“…The pellet was resuspended in 50 mM Tris HCl/l mM MgCl2, pH 7.4, and stored at -70°C; the supernatant of the original 40,000 g centrifugation was transferred to 16 x 102-mm polyallomer tubes (Beckman) and centrifuged at 125,000 g for 24 h at 4°C in a Beckman L350 ultracentrifuge. For assay, 80 Al ofeach cell fraction preparation was incubated with 10 s1 of(+)'251-iodocyanopindolol (ICYP), which has binding characteristics similar to (-)-'251-ICYP (26), at a final concentration ranging from 20 to 200 pM, in a total volume of 100 Ml at 37°C, in 12 X 75-mm polypropylene tubes for 30 min., at which time the plateau ofthe binding reaction was reached. Nonspecific binding was assessed by the addition of 1 MM (-)-propranolol (final concentration).…”