Analysis of dose-response curves and calculation of agonist dissociation constants using a weighted nonlinear curve fitting program

An operational model of pharmacological agonism: the effect of E/[A] curve shape on agonist dissociation constant estimation

“…This result should hold generally and indeed was a feature of the data presented here. McPherson et al (1983), in their analysis of padrenoceptor irreversible antagonism by Ro 03-7894, assume that the pre-and post-inactivation curves should have the same gradient even although they are inherently steep. Having shown by computer simulation that Furchgott's method does not hold in these circumstances, they deduced that the irreversible antagonism method is not applicable for non-hyperbolic E/[A] curves.…”

“…In neither case do the interpolated concentrations necessarily correspond to 'real' data points and differences in the choice of interpolations introduces differences in precision of KA estimation (Thron, 1970). The optimal way of analysing data by the Furchgott method appears to be that described by McPherson et al (1983) in which both pre-and post-inactivation E/ [A] curves are fitted by a logistic function. However, the validity of using the logistic function may be questioned as it can be proven (see Appendix) that there is no single definable transducer function which can translate a set of rectangular hyperbolic occupancy functions with varying [RO]s into a corresponding set of logistic E/[A] relations.…”

“…In the latter circumstances particularly, theoretical expectation of E/ [A] curve shape behaviour with variable [R.] is relevant in order to establish conditions under which estimation of KAs are valid. In a recent paper (McPherson et al, 1983) the absence of such a framework for expectation led to the assertion that 'to calculate accurate KA values it is essential that the pre-and post-inactivation concentration-response curves [in the method of Furchgott (1966)] be rectangular hyperbolas', a claim which contravenes the principle of the null methods (for reviews see Colquhoun, 1973;Jenkinson, 1978).…”

Structural Determinants of Aldosterone Binding Selectivity in the Mineralocorticoid Receptor

“…Scatchard analysis was performed on the MR LBD, GMGG, and GMGM chimeras using [ 3 H]aldosterone at concentrations of 0.26, 0.64, 1.6, 4, 10, and 20 nM. Each point was assayed in triplicate, and data was analyzed using the EBDA program (20). To measure GR-type binding 10 nM [ 3 H]dexamethasone was used, and nonspecific binding was assessed by adding a 500-fold excess of non-radioactive dexamethasone.…”

Characterization of histamine‐H3 receptors controlling non‐adrenergic non‐cholinergic contractions of the guinea‐pig isolated ileum

“…Apparent agonist affinity (pKD) values were estimated by the null method of Furchgott using a weighted non-linear curve-fitting programme (McPherson et al, 1983). H3 receptor antagonist-induced parallel displacement of RAMH concentration-effect curves was quantified as the ratio 0.5g…”