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Characterization of β ‐adrenoceptors in urinary bladder: comparison between rat and rabbit
Author(s) -
Oshita Masafumi,
Hiraoka Yasuko,
Watanabe Yoshinari
Publication year - 1997
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0701562
Subject(s) - isoprenaline , propranolol , endocrinology , medicine , schild regression , chemistry , urinary bladder , agonist , urinary system , stimulation , receptor , biology
1 β‐Adrenoceptor subtypes in rat and rabbit urinary bladder were investigated in functional experiments by use of several agonists and antagonists. 2 All agonists tested produced concentration‐dependent relaxation, but the relative potencies varied between both species: BRL 37344 (pD 2 :8.0)>isoprenaline (7.3)>adrenaline (6.7)=noradrenaline (6.6) in rat bladder, and isoprenaline (8.7)=adrenaline (8.5)>noradrenaline (7.7)=BRL 37344 (7.4) in rabbit bladder. 3 The relaxation response to isoprenaline in rat bladder was relatively resistant to propranolol and ICI 118551, and the slopes of Schild plot for both antagonists were different from unity. The apparent p K B values estimated by single concentrations of propranolol (1, 10 μ m ) and ICI 118551(10 μ m ) were 6.6 and 5.4, respectively. 4 On the other hand, the relaxation response to isoprenaline in rabbit bladder was antagonized by lower concentrations (1 n m –100 n m ) of propranolol and ICI 118551 in a competitive manner, resulting in pA 2 values of 8.7 and 8.6, respectively. 5 These results suggest species‐heterogeneity of β‐adrenoceptors in urinary bladder; β 3 and β 2 subtypes in rat and β 2 subtype in rabbit.