Light and electron microscopic studies of rat kidney after administration of inhibitors of the citric acid cycle in vivo. II. Effects of sodium malonate on proximal convoluted tubule.

The morphologic changes that occurred in the proximal convoluted tubule of the rat after sodium malonate at 888 mg and 1776 mg kg of body weight was injected have been studied by light and electron microscopy. Mitochondrial matrix swelling and loss of matrix granules and an increase in the smoothsurfaced endoplasmic reticulum were early changes. Varying degrees of cytoplasmic rarefaction occurred during the first 3 hours. Marked cytoplasmic swelling occurred only in female rats. Intracristal dilatation accompanied cytoplasmic rarefaction but there was no evidence that the mitochondrial matrix was condensed as judged by its electron density. During the early stages, dilatation of the rough endoplasmic reticulum was not necessarily associated with cytoplasmic rarefaction but varying degrees of dilatation occurred at later time intervals in the swollen cells. The changes appeared for the most part to be reversible. Focal areas of tubular necrosis occurred in a few rats.