Determining the parameters of concentration-response relationship for histamine on the isolated portion of guinea pig stomach and guinea pig right atrium.

摘要

In our previous experiments measuring acid secretion in the isolated mouse stomach we found higher EC50 values (agonist concentration, evoking half maximal effect) for histamine than in the experiments on the isolated guinea pig right atrium (contraction frequency). The difference could be due to nonequilibrium conditions in the isolated mouse stomach preparation or to species differences. In order to check this possibility and to test the consistency of concentration-response relationship (CRR) parameter determination on an isolated secretory organ, we compared EC50 for histamine and pA2 for famotidine on the two isolated preparations from the same species, guinea pigs. Both, EC50 and pA2 values were significantly different when measuring gastric acid secretion (9.7 microM and 6.07) from the parameters, found in the isolated right atrium measuring frequency of contractions (1.6 microM and 7.06). From these results it can be concluded that the isolated portion of guinea pig stomach is suitable for CRR determination; but the parameters obtained are in the range of higher concentrations than the real ones because of kinetic particularities of the preparation.