Analysis of apparent co-operativity in the catecholamine-stimulated lipolysis of rat adipose tissue.
(1) The methods available for assessment of the regulatory features of dose-response relationships that do not conform to the Hill equation are considered, and the sensitisation index Si introduced (2) The value of determining Si is assessed using lipolytic dose-response relationships yielded by beta-adrenergic agonists both alone and in the presence of their specific antagonists [D. M. F. Cooper and J. I Davies, Biochem. Pharmac. 31, 721 (1982)]. (3) It is shown that where the Hill equation is fitted to relationships between L-noradrenaline concentration and lipolysis, the high value obtained for the Hill coefficient (1.69) is artefactual (4) By fitting a rational quadratic model and evaluating Si, a solution is obtained (Si(max), 1.02) which is free of this artefact. (5) The relationship between the results obtained by analysis of dose-response curves and direct binding of catecholamine analogues to membrane receptors is discussed.
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008066:Lipolysis / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats
D002395:Catecholamines; D011433:Propranolol; D009638:Norepinephrine