cl-316243 and cyanopindolol

This study examines the action of the beta(3)-adrenoceptor antagonist SR59230A [3-(2-ethylphenoxy)-1-[(1,S)-1,2,3,4-tetrahydronapth-1-ylamino]-2S-2-propanoloxalate] at cloned mouse beta(3)-adrenoceptors expressed in Chinese hamster ovary cells (CHO-K1-beta(3)) or endogenously expressed in 3T3-F442A adipocytes or ileum. SR59230A displayed partial agonist properties compared with the beta(3)-adrenoceptor agonist CL316243 [(R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate] in CHO-K1-beta(3) with the intrinsic activity increasing with the level of receptor expression. Functional affinity values for SR59230A at each level of receptor expression were in agreement with pK(I) values determined by binding. In cytosensor microphysiometer studies, SR59230A was a full agonist for increases in extracellular acidification rates (ECARs) at all levels of receptor expression, and antagonist actions were measurable only in medium- or low-expressing cells. In 3T3-F442A adipocytes, SR59230A antagonized CL316243-mediated increases of cAMP and had no agonist actions. However, in the cytosensor micro-physiometer, SR59230A (acting via beta(3)-adrenoceptors) was an agonist with an intrinsic activity greater than CL316243. In mouse ileum, SR59230A relaxed smooth muscle, although concentration-response curves were biphasic. Relaxant effects were produced by concentrations that did not affect cAMP levels. Differences in tissue responses to SR59230A were not caused by major differences in expression of Galphas. ECAR responses were not affected by pretreatment of cells with pertussis toxin, indicating that signaling did not involve Gi. Therefore, SR59230A displays agonist and antagonist actions at the mouse beta(3)-adrenoceptor. Because SR59230A only antagonized accumulation of cAMP in 3T3-F442A adipocytes yet in the same cells was an agonist for ECAR, cAMP-independent signaling pathways must mediate part of the agonist actions in the microphysiometer.

Topics: 3T3 Cells; Adipocytes; Adrenergic beta-3 Receptor Agonists; Adrenergic beta-3 Receptor Antagonists; Adrenergic beta-Antagonists; Animals; CHO Cells; Cricetinae; Cyclic AMP; Dioxoles; GTP-Binding Protein alpha Subunits, Gi-Go; GTP-Binding Protein alpha Subunits, Gs; Ileum; Mice; Pindolol; Propanolamines

1. This study examines beta(1)-, beta(2)- and beta(3)-adrenoceptor (AR)-mediated responses, mRNA levels and radioligand binding in ileum from beta(3)-AR knock-out (-/-) (KO) and wild type (+/+) (FVB) mice. 2. In KO and FVB mice, SR59230A (100 nM) (beta(3)-AR antagonist) antagonized responses to (-)-isoprenaline in both KO and FVB mice. (-)-Isoprenaline mediated relaxation of ileum was antagonized weakly by ICI118551 (100 nM) (beta(2)-AR antagonist). Responses to (-)-isoprenaline were more strongly antagonized by CGP20712A (100 nM) (beta(1)-AR antagonist), propranolol (1 microM) (beta(1)-/beta(2)-AR antagonist), carvedilol (100 nM) (non-specific beta-AR antagonist), and CGP12177A (100 nM) (beta(1)-/beta(2)-AR antagonist) in ileum from KO than in FVB mice. 3. Responses to CL316243 (beta(3)-AR agonist) in ileum from FVB mice were antagonized by SR59230A (100 nM) but not by propranolol (1 microM) or carvedilol (100 nM). CL316243 was ineffective in relaxing ileum from KO mice. 4. CGP12177A had no agonist actions in ileum from either KO or FVB mice. 5. beta(1)-AR mRNA levels were increased 3 fold in ileum from KO compared to FVB mice. This was associated with an increased maximum number of beta(1)-/beta(2)-AR binding sites (B(max)). beta(2)-AR mRNA levels were unaffected while no beta(3)-AR mRNA was detected in KO mice. 6. In mouse ileum, beta(3)-ARs and to a lesser extent beta(1)-ARs are the predominant adrenoceptor subtypes mediating relaxation in ileum from FVB mice. In KO mice beta(1)-ARs functionally compensate for the lack of beta(3)-ARs, and this is associated with increased beta(1)-AR mRNA and levels of binding.

Topics: Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Animals; Dioxoles; Genotype; Ileum; In Vitro Techniques; Isoproterenol; Mice; Mice, Knockout; Muscle Relaxation; Muscle, Smooth; Pindolol; Propranolol; Receptors, Adrenergic, beta-1; Receptors, Adrenergic, beta-3; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger

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 > selective 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 CL 316243 was not. Cyanopindolol, a non-selective beta-adrenoceptor antagonist, antagonized CL 316243-induced relaxation in a competitive manner with a pA2 of 6.10, and this value was lower than that when salbutamol was used as an agonist (6.69). Intracellular cAMP levels were increased by CL 316243, an effect that was not altered by ICI 118551. Therefore, beta 3-adrenoceptors may be present and functioning in canine pulmonary artery.

Topics: Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Albuterol; Animals; Cyclic AMP; Dioxoles; Dogs; Ethanolamines; Female; In Vitro Techniques; Isoproterenol; Male; Muscle Relaxation; Muscle, Smooth, Vascular; Pindolol; Propanolamines; Pulmonary Artery; Receptors, Adrenergic, beta; Receptors, Adrenergic, beta-3

1. We have previously shown (Malinowska & Schlicker, 1996) that the atypical beta-adrenoceptor involved in the positive chronotropic effect of the so-called non-conventional partial beta-adrenoceptor agonists CGP 12177 and cyanopindolol in the pithed rat possesses properties markedly different from those observed for beta3-adrenoceptors in the literature. In the present study, we have directly compared the pharmacological properties of the atypical cardiostimulant beta-adrenoceptor and of the beta3-adrenoceptor mediating the thermogenic response in the brown adipose tissue in pithed and vagotomized rats. 2. Heart rate was dose-dependently increased by CGP 12177 and cyanopindolol by maximally 150 and 100 beats min(-1), yielding pED50 values of 8.0 and 7.3, respectively (pED50, -log10 of the dose in mol kg(-1) body weight i.v. causing the half-maximum effect), but not affected by the selective beta3-adrenoceptor agonist CL 316243 (pED50 > 6.0). 3. CGP 12177, cyanopindolol and CL 316243 increased temperature in the brown adipose tissue by maximally 1 degree C (pED50 values 7.4, 6.3 and 8.6, respectively). 4. The beta1-adrenoceptor antagonist CGP 20712 10 micromol kg(-1), attenuated the cardiostimulatory effect of CGP 12177 and, at a still higher dose (30 micromol kg(-1)), also antagonized its thermogenic effect. The -log10 values of the doses causing a two fold shift of the dose-response curves (DRCs) of CGP 12177 to the right were 6.1 and 5.2, respectively, and were much lower than the corresponding value for the antagonism of CGP 20712 against the beta1-adrenoceptor-mediated positive chronotropic effect which was 8.6. 5. The cardiostimulant and the thermogenic effect of CGP 12177 were not affected by the beta2-adrenoceptor antagonist ICI 118551 10 micromol kg(-1). 6. The beta3-adrenoceptor antagonist SR 59230A (which, by itself, caused a beta1-adrenoceptor-mediated increase in heart rate and, for this reason, was studied after administration of a low dose of CGP 20712) attenuated the cardiostimulant and the thermogenic effect of CGP 12177 to a similar extent. The -log10 values of the doses causing two fold rightward shifts of the DRCs of CGP 12177 were 5.9 and 5.7, respectively. 7. The non-selective beta-adrenoceptor antagonist bupranolol diminished the cardiostimulant and thermogenic response to a very similar extent. The -log10 values causing two fold rightward shifts of the DRCs of CGP 12177 were 5.6 and 5.7, respectively, and were much lower than the c

Topics: Adipose Tissue, Brown; Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Animals; Dioxoles; Dose-Response Relationship, Drug; Heart Rate; Imidazoles; Male; Pindolol; Propanolamines; Rats; Rats, Wistar; Temperature

The rat gastric fundus is known to possess an "atypical" beta-adrenergic receptor that mediates relaxation to isoproterenol. The purpose of this study was to characterize the relationship between this "atypical" beta receptor in the rat stomach and the cloned rat beta 3 receptor by taking advantage of highly selective pharmacological and molecular biological probes of the beta 3 receptor. Nuclease protection analysis of RNA from the rat gastric fundus identified beta 3 receptor mRNA whose levels in the stomach were exceeded only by those in adipose tissue. Pharmacological analysis of the recombinant rat beta 3 receptor expressed in Chinese hamster ovary cells indicated low affinity of propranolol with a Ki value of 2.3 microM. Therefore, 0.3 microM propranolol was chosen as a concentration that would completely block beta 1 and beta 2 receptors (Ki = 1-5 nM) but would leave beta 3 receptors largely intact in the rat stomach fundus. In the presence of propranolol, several beta-adrenergic receptor agonists relaxed the rat stomach fundus with a rank potency order of (R,R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethyl]-amino]-propyl]1,3- benzodioxole-2,2-dicarboxylate (CL316,243) > isoproterenol > norepinephrine = epinephrine = dl-4-3[(1,1-dimethylethyl)amino]-2- hydroxylproproy]1,3 dihydro-2H-benzimidazol-2-one hydrochloride (CGP12177) > clenbuterol > terbutaline > pindolol. Isoproterenol, norepinephrine and epinephrine were full agonists, whereas (R,R)-5-[2-[[2-(3-chlorophenyl)-2- hydroxyethyl]-amino]-propyl]1,3-benzodioxole-2,2-dicarboxylate was only a partial agonist with 66% intrinsic activity relative to isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenylyl Cyclases; Animals; CHO Cells; Cricetinae; Dioxoles; Enzyme Activation; Gene Expression; In Vitro Techniques; Male; Muscle Relaxation; Pindolol; Propranolol; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, beta; RNA, Messenger; Stomach