The Effect of Hyperthyroidism on Rat Atria Intracellular Potentials

Abstract

The effect of thyroid hormone pretreatment on intracellular potentials recorded from isolated rat atria has been investigated. Recordings were made by conventional intracellular recording techniques and it was found that in spontaneously beating right atria from thyroxine treated rats both the resting membrane potential and the 95% repolarization times were reduced. Atria from treated animals beat much faster than those from controls but only part of the changes seen resulted directly from this for both variables were statistically significantly reduced in treated atria driven at 240 beats/minute i.e. above the maximum spontaneous rate observed.

It was suggested that the electrophysiological changes seen might partially account for the arrhythmias associated with hyperthyroidism.

Key words

Thyroxine - Atria - Intracellular Potentials - Tachycardia

1 Present address: Faculty of Pharmacy, Mahidol University, Phyathai, Sri-Ayuthaya Road, Bangkok, Thailand

2 Present address: Department of Pharmacology, Faculty of Medicine, University of British Columbia, Vancouver 8, Canada