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Effect of steroids on β‐adrenoceptor‐mediated relaxation of pig bronchus
Author(s) -
Foster Paul S.,
Goldie Roy G.,
Paterson James W.
Publication year - 1983
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 - 10.1111/j.1476-5381.1983.tb09409.x
Subject(s) - potency , fenoterol , isoprenaline , normetanephrine , chemistry , endocrinology , medicine , guinea pig , tranylcypromine , pharmacology , catecholamine , biology , biochemistry , enzyme , in vitro , monoamine oxidase , stimulation , asthma
1 Progesterone, testosterone (40 μ m ), cortisol and cortisol hemisuccinate (80 μ m ) caused 6–8 fold potentiations of (±)‐isoprenaline (Iso)‐induced relaxations of pig bronchus while several other steroids caused smaller potentiations or had no effect. 2 17β‐Oestradiol (40 μ m ) increased the potency of Iso, (−)‐adrenaline (Adr) and (−)‐noradrenaline (NA) by 10.6, 2.3 and 2.6 fold respectively but had no significant effect on the potency of fenoterol (Fen). 3 Inhibition of catechol‐ O ‐methyl transferase (COMT) with U‐0521 (30 μ m ) caused a 6 fold increase in the potency of Iso but failed to alter the potency of Adr, NA or Fen. The extraneuronal uptake inhibitor normetanephrine (50 μ m ) caused significant 2 fold increases in the potency of Iso and Adr but did not potentiate the responses to NA or Fen. 4 In preparations where the potency of Iso had already been increased by U‐0521 (30 μ m ) or by normetanephrine, 17β‐oestradiol produced no significant further increase in potency. These results indicate that steroid‐induced increases in the potency of catecholamines in pig bronchus can be explained in terms of inhibition of COMT or extraneuronal uptake or both.