The influence of thyroid hormones on normal rat-liver mitochondria III. Thyroxine-induced swelling in pretreated mitochondria

Abstract

1. 1. Thyroxine caused swelling in rat-liver mitochondria which had been pretreated with deionized H 2O and then added to sucrose, phosphate-buffered media. The resulting structural changes were observed in short-term incubations and were enhanced markedly by the addition of adenosine 5′-diphosphate. Adenosine 5′-triphosphate also permitted thyroxine-induced swelling, but the latent period prior to this swelling was greater than when adenosine 5′-diphosphate was used. 2. 2. In the presence of adenosine 5′-diphosphate the swelling was correlated with a loss of respiratory control, although it occurred after the initial stimulation of the rate of O 2 uptake by thyroxine. With adenosine 5′-triphosphate the swelling accompanied thyroxine-stimulated adenosine-5′-triphosphatase activity. The data support the concept that both adenosine-5′-triphosphatase activity and mitochondrial swelling are released by the breakdown of high-energy intermediates.