[Behaviour of the aortic lipoidosis in rats twenty months after the withdrawal of an hyperlipidic diet (author's transl)].

48 rats were placed on an hyperlipidic diet (cholesterol, cholic acid, cholin, propylthiouracil), 23 were sacrificed at various intervals from the fourth up to the twelve month of the experiment. In the remaining 25 rats, the atherogenic regimen was replaced by a normal one. These animals were sacrificed one to twenty months after the withdrawal of the experimental diet. Aortae of experimental and control animals were studied by means of histological and histochemical technics. All the animals developed hypercholesterolemia together with intima and media lipoidosis. None demonstrated any aortic cell proliferation. The only metabolic change of the smooth muscle cell was a progressive decrease in 5' nucleotidase, acid esterase and cholinesterase activities. The return to a normal diet involved the reversion of the serum cholesterol level to normal values and the disappearance of intima lipoidosis. The reduced enzymatic activities in the media returned to normal levels around the six month. The surfaces of the extracellular sudanophilic areas decreased. However, twenty months after the withdrawal of the atherogenic diet, some lipids still persisted at the edges of the elastic fibres.