Effects of salmon calcitonin on SA nodal pacemaker activity and contractility in isolated, blood-perfused atrial and papillary muscle preparations of dogs.

Effects of salmon calcitonin on SA node pacemaker activity and contractility were investigated in isolated atrium and papillary muscle preparations which were perfused with arterial blood led from a carotid artery of the support dog. Calcitonin at a dose range from 0.005 to 0.16 units was injected into the cannulated sinus node artery, which dose-relatedly caused a negative chronotropic and inotropic effect in atrium preparations. This negative effect was not modified by treatment with atropine. On the other hand, in the isolated paillary muscle preparations, an intraarterial calcitonin caused little negative inotropic effect even at higher dose level of 0.16 units. From these results, it is concluded that 1) in chronotropy, calcitonin causes a negative chronotropic effect, and 2) in inotropy calcitonin causes a negative inotropic effect on the atrium but not on the ventricle.