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Lipomobilizing effects of procaterol and yohimbine in the conscious dog: comparison of endocrinological, metabolic and cardiovascular effects
Author(s) -
Valet Philippe,
Taouis Mohammed,
Tran Marie A.,
Montastruc Paul,
Lafontan Max,
Berlan Michel
Publication year - 1989
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.1476-5381.1989.tb11946.x
Subject(s) - yohimbine , endocrinology , medicine , lipolysis , chemistry , stimulation , agonist , heart rate , antagonist , blood pressure , adipose tissue , receptor
1 Lipid mobilization during a hypocaloric diet may be enhanced by a pharmacological approach using β 2 ‐adrenoceptor agonists or α 2 ‐adrenoceptor antagonists. Studies were undertaken in the dog, an animal model presenting fat cell antilipolytic α 2 ‐ and lipolytic β‐adrenoceptors, in order, firstly, to demonstrate the presence of β 2 subtype adrenoceptors on adipocytes and, secondly, to compare the effects of procaterol (β 2 ‐adrenoceptor agonist) and of yohimbine (α 2 ‐adrenoceptor antagonist) on metabolic, endocrinological and cardiovascular parameters. 2 Procaterol strongly stimulates lipolysis in dog adipocytes in vitro . The utilisation of selective β 1 ‐ and β 2 ‐adrenoceptor antagonists (bisoprolol and ICI 118,551) in both lipolysis and binding studies (displacement of [ 3 H]‐dihydroalprenolol binding) demonstrated the presence of the two β‐adrenoceptor subtypes in dog fat cells. 3 Infusion of either yohimbine or procaterol (10 and 0.4 nmol min −1 kg −1 , respectively for 30min). provoked an equivalent increase in plasma non‐esterified fatty acids (+100%). Procaterol, but not yohimbine, induced hyperglycaemia (+ 120%). Plasma insulin was weakly enhanced by yohimbine (+ 120%) as compared to the increase given by procaterol (+ 500%). 4 Both drugs stimulated sympathetic nervous system activity, as indicated by the increased plasma noradrenaline concentration, but only yohimbine increased the plasma adrenaline level. 5 Cardiovascular measurements indicated that procaterol strongly enhances heart rate and transiently decreases mean blood pressure. Yohimbine exhibits a weaker effect on heart rate and slightly increases mean blood pressure. 6 The present work clearly indicates that lipid mobilization is enhanced during fasting in the dog by selective β 2 ‐adrenoceptor stimulation or by α 2 ‐adrenoceptor blockade. This enhanced lipolytic effect may result either from a direct action of the drugs on the adrenoceptors of fat cells or from an activation of the sympathetic nervous system. Procaterol suffers major limitations since it strongly increases heart rate, immunoreactive insulin and glycaemia. On the other hand, yohimbine induces only minor modifications both in cardiovascular and endocrinological parameters.