[Pharmacodynamics of luteolin-histamine and receptors response]

The isolated guinea pig ileum were used to investigate the pharmacodynamics of the relationship between luteolin and histamine dose response. The pharmacodynamics parameters were estimated by various methods. The values of the pA2, the slope and the pD'2 were 5.6, 0.6 and 4.4, respectively. The dissociation constants and the maximal response were estimated by the Lineweaver-Burk, Hanes-Woolf, Scatchard or Woolf methods. The estimated values of the parameters were: EAmax not equal to EABmax, KA not equal to alpha KA, KB not equal to alpha KB. The linear intersecting points of the plotting by the Lineweaver-Burk method were above X axis (2nd or 1st quadrant), by the Hanes-Woolf method were below X axis (3rd quadrant), by the Scatchard method were below X axis (4th quadrant) and by the Woolf method were to the left of Y axis (2nd quadrant). The antagonistic action of luteolin is assumed to be noncompetitive and competitive in combination. The estimated Hill coefficient approached to 1 which is accorded with the M-M formula. Although any one of the four linear transformation method of the M-M equation could be used to estimate the dissociation constants and the maximal responses, there exists difference between them. The values of the parameters obtained by the Lineweaver-Burk method were excessively large (eg, EAB2max = 360.3, KAB2 = 28.4), even negative (eg, alpha KB1 = -7.9, alpha KB2 = -14.6), and so it is inferior to the other three methods, as reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)