Ultrastructural changes in kidney, myocardium and skeletal muscle of the dog during excessive mobilization of free fatty acids

Abstract

Ultrastructural changes have been studied in kidney, myocardium and skeletal muscle of dogs during excessive mobilization of free fatty acids induced by continuous infusion of noradrenaline. A special type of cytoplasmic body appears in all three organs. Because of the close correspondence with respect to size, localization and frequency between these bodies and simultaneously appearing sudanophilic droplets in light microscopical preparations, they are referred to as “lipid bodies” and assumed to represent triglyceride deposited as the fatty acids taken up by the cells become esterified. In the kidney, most lipid bodies are seen in the proximal tubule epithelium. In the heart, they appear in all fibers, whereas in skeletal muscle, there are fibers with abundant, moderate and slight amounts. There are no obvious connections between the lipid bodies and cytomembranes or sarcotubular system. However, especially in myocardium and skeletal muscle but also to some extent in the kidney, mitochondria are seen in close proximity to lipid bodies. There seems to be no membrane structure around lipid bodies which in the present series contained a material with varying electron density. No information about the mechanisms for uptake and transport of fatty acids into cells was obtained. There was no obvious damage to the cell structures including the mitochondria, in spite of the marked change in intensity and distribution of the succinic dehydrogenase reaction in light microscopical preparations.