Absence of Acute Cardiac Effect of Triiodothyronine in Isolated, Blood-perfused Canine Atrium

抄録

Effects of triiodothyronine (T₃) on SA node pacemaker activity, atrial contractility and on chronotropic and inotropic responses to norepinephrine were investigated, using 9 isolated, blood-perfused dog atrium preparations. T₃ (0.001pg-0.1μg) did not cause a significant direct action injected into the cannulated sinus node artery. When T₃ (10pg/min, 40pg/min, 0.1μg/min, or 0.4μg/min) was continuously infused into the sinus node artery, both positive chronotropic and inotropic actions of norepinephrine (0.03μg-0.3μg) were not influenced.
From these results, it is concluded that T₃ has neither acutely direct chronotropic nor inotropic effects, and also T₃ does not have an acute effect on responses to norepinephrine in the isolated, blood-perfused canine atrium.