Avtor/Urednik		Mohar, Urša; Stanovnik, Lovro
Naslov		Comparison on two methods for pA2 determination in two types of guinea pig isolated preparations, bearing H2 receptors
Tip		članek
Vir		Period Biol
Vol. in št.		Letnik 107, št. 2
Leto izdaje		2005
Obseg		str. 157-64
Jezik		eng
Abstrakt		Background and Purpose: Isolated stomach, frequently used for studying histamine H2 antagonists, shows some properties that render it less suitable for determining pA2 values of antagonists by Schild analysis. We tried to find out whether a new method, introduced by Calderone, could be more reliable for pA2 determination on the isolated stomach. Material and Methods: Calderone and Schild analysis were applied for two H2 antagonists, famotidine and tiotidine, in guinea pig isolated stomach and right atrium. Both organs bear H2 histamine receptors, but show different types of responses and different kinetic properties. The pA2 and the slope of the regression line were determined by Calderone analysis. For tiotidine, Schild analysis was also applied. Changes in rate of acid secretion were measured in the stomach and the changes in contraction frequency in the atrium. Results: The data from the isolated stomach showed high variability, regardless of the method used. With tiotidine, the value of pA2 did not differ significantly between the two methods, or between the preparations. The slopes of regression lines were not different from unity. For famotidine, Calderone analysis did not show any differences in parameters between the preparations in contrast to the results of the Schild analysis. With tiotidine, a direct comparison of histamine concentration-response curves in the absence and in presence of the antagonist indicated insurmountable antagonism. Conclusion: We can conclude that Calderone analysis has no advantage in comparison to the Schild method in the isolated stomach preparation. In our work this analysis did not reveal the insurmountable nature of tiotidine.
Deskriptorji		STOMACH HEART ATRIUM HISTAMINE H2 ANTAGONISTS FAMOTIDINE GASTRIC ACIDITY DETERMINATION GUINEA PIGS MYOCARDIAL CONTRACTION REGRESSION ANALYSIS