Effects of chronic absorption of dietary supplements of methionine and cystine on arterial morphology in the rat

Abstract

Male Wistar rats were fed diets containing supplements of either methionine or cystine from 10 weeks of age and compared to rats fed a control diet or a high protein diet kept under identical conditions. At 11–16 months of age, the aorta and the renal, iliac and caudal arteries of all rats were fixed and examined by light and electron microscopy. Cystine-fed rats showed arterial morphology similar to that of control rats and of those having received a high protein diet. Methionine-fed rats showed marked thickening of the arterial wall which was due, on the one hand, to massive intimal thickening, as a result of accumulation of granular material in the subendothelial region and, on the other hand, to marked thickening of the media as a result of increased extracellular material around smooth muscle cells. Zones of early phases of chondroid metaplasia were also observed in the media. Thus cystine and methionine, despite their interrelated metabolism, have very different effects on the morphology of the arterial wall. However, cystine and methionine both inhibited the spontaneous rupture of the internal elastic lamina in the renal artery. This latter result is discussed in the light of the similarities between spontaneous rupture of the internal elastic lamina and β-aminopropionitrile-induced aortic aneurysm and rupture.