Dahlia et al. reported that increasing the concentration of Ca in the bathing medium from 0.625 mM to 2.5 mM decreased response of rat ventricle to norepinephrine, but Sullivan et al. showed that variation of Ca concentration between 0.15 mM and 2.4 m...
Dahlia et al. reported that increasing the concentration of Ca in the bathing medium from 0.625 mM to 2.5 mM decreased response of rat ventricle to norepinephrine, but Sullivan et al. showed that variation of Ca concentration between 0.15 mM and 2.4 mM had no significant effect on response of rabbit aortic strips to norepinephrine.
In order to investigate the influence of Ca concentration on responses of the isolated organs of norma and reserpinized rabbits to catecholamines, author observed the contractile responses of the isolated atria, aortic strips, splenic capsules and vas deferenses of normal and reserpinized rabbits to epinephrine and norepinephrine in Locke-Ringer bathing medium containing 1.2 mM and 2.4 mM Ca respectively.
The results obtained were summarized as follows:
1. In 1.2 mM Ca Locke-Ringer medium than normal Locke-Ringer medium (containing 2.4 mM Ca). responses of isolated atria and aortic strips of normal rabbits to both epinephrine and norepinephrine were more significantly increased, and responses of vas deferenses not significantly increased, but responses of splenic capsules rather decreased.
2. In normal Locke-Ringer medium, responses of isolated atria, aortic strips and vas deferenses to both catecholamines were significantly increased by reserpine pretreatment, but by decrease of calcium concentration in Locke-Ringer medium to 1.2 mM, the increase of the responses by reserpine pretreatment were not affected.