Effects of Picloram on Mitochondrial Swelling and ATPase

Abstract

Effects of 4-amino-3,5,6-trichloropicolinic acid (picloram) on mitochondrial volume changes and ATPase activity were studied with isolated barley (Hordeum vulgareL., var. Wong) and safflower (Carthamus tinctoriusL., var. U. S. 10) mitochondria. Changes in mitochondrial volume and/or configuration of mitochondrial membranes were recorded in terms of changes in light scattering, which was expressed as absorbance. Picloram caused swelling of mitochondria previously contracted by ATP. Picloram-induced swelling was characterized by a later partial recovery of the mitochondria to a contracted state. Picloram did not affect succinate-induced contraction nor cause any additional swelling of the mitochondria in 0.3 M KCl medium. A high concentration (10−3M) of picloram enhanced the activity of ATPase by 31%. This result was consistent with an increased rate of picloram-induced swelling in mitochondria contracted earlier by ATP. The action of picloram apparently differs from that of known mitochondrial swelling agents.