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The effects of SB 216469, an antagonist which discriminates between the a1A-adrenoceptor and the human prostatic a1-adrenoceptor

The effects of SB 216469, an antagonist which discriminates between the a1A-adrenoceptor and the human prostatic a1-adrenoceptor. Chess-Williams, R.; Chapple, C.Some chemicals with cas registry numbers like 152735-23-4 are also used. R.; Verfurth, F.; Noble, A. J.; Couldwell, C. J.; Michel, M. C. (Department Biomedical Science, University Sheffield, Sheffield, UK). British Journal of Pharmacology, 119(6), 1093-1100 (English) 1996 Stockton. CODEN: BJPCBM. ISSN: 0007-1188. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) Section cross-reference(s): 2 The affinity of the a1-adrenoceptor antagonist SB 216469 (also known as REC 15/2739) has been detd. at native and cloned a1-adrenoceptor subtypes by radioligand binding and at functional a1-adrenoceptor subtypes in isolated tissues. In radioligand binding studies with [3H]-prazosin, SB 216469 had a high affinity at the a1a-adrenoceptors of the rat cerebral cortex and kidney (9.5-9.8) but a lower affinity at the a1b-adrenoceptors of the rat spleen and liver (7.7-8.2). At cloned rat a1-adrenoceptor subtypes transiently expressed in COS-1 cells and also at cloned human a1-adrenoceptor subtypes stably transfected in Rat-1 cells, SB 216469 exhibited a high affinity at the a1a-adrenoceptors (9.6-10.4) with a significantly lower affinity at the a1b-adrenoceptor (8.0-8.4) and an intermediate affinity at the a1d-adrenoceptor (8.7-9.2). At functional a1-adrenoceptors, SB 216469 had a similar pharmacol. profile, with a high affinity at the a1A-adrenoceptors of the rat vas deferens and anococcygeus muscle (pA2=9.5-10.0), a low affinity at the a1B-adrenoceptors of the rat spleen (6.7) and guinea-pig aorta (8.0), and an intermediate affinity at the a1D-adrenoceptors of the rat aorta (8.8). Several recent studies have concluded that the a1-adrenoceptor present in the human prostate has the pharmacol. characteristics of the a1A-adrenoceptor subtype. However, the affinity of SB 216469 at human prostatic a1-adrenoceptors (pA2=8.1) detd. in isolated tissue strips, was significantly lower than values obtained at either the cloned a1a-adrenoceptors (human, rat, bovine) or the native a1A-adrenoceptors in radioligand binding and functional studies in the rat. Our results with SB 216469, therefore, suggest that the a1-adrenoceptor mediating contractile responses of the human prostate has properties which distinguish it from the cloned a1a-adrenoceptor or native a1A-adrenoceptor. Since it has previously been shown that the receptor is not the a1B- or a1D-adrenoceptor, the functional a1-adrenoceptor of the human prostate may represent a novel receptor with properties which differ from any of the a1-adrenoceptors currently defined by pharmacol. means. .