Effect of Digoxin on Chick Embryos with Hyperthyroidism Induced by L-Thyroxin

Yuji Yoshiyama1, Tomoko Misaki2 and Takashi Sugiyama2

1 Division of Clinical Pharmacy, Kyoritsu University of Pharmacy, 1-5-30, Shibakoen, Minato-ku, Tokyo 105-8512, Japan
2 Division of Pathophysiology, Center for Clinical Pharmacy and Clinical Sciences, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo 108-8641, Japan

AATEX 11(2):105-111, 2005

The objective of this study was to demonstrate that the chick embryo with hyperthyroidism induced by treatment with L-thyroxin (TRX) was a feasible model as an alternative to animal model and to examine the pharmacological effects of digoxin using this model. When 0.5 or 1.0 g/egg of TRX was injected into the eggs, the 16th day-chick embryos showed some characteristic changes including an increased heart rate (tachycardia), an increased relative heart weight (cardiac hypertrophy) and relative thyroid weight (thyroid hypertrophy), and an increased concentration of plasma T3 and T4. These findings sug-gest that TRX-treated chick embryos may be a model of the heart diseases associated with hyperthy-roidism. When 50 g/egg of digoxin was injected into the TRX-treated eggs, negative chronic action reduced. This fact suggests that digoxin decreased the sensitivity to TRX in the heart of chick embryos with hyperthyroidism as well as in dog and man. In conclusion, the TRX-treated chick embryos may prove to be an alternative to animal experiments to predict unexpected effects of cardiovascular drugs.

Key words: Chick embryo; hyperthyroidism; thyroxin; digoxin; electrocardiogram