Capillary size, density and ultrastructure in brain of rats with urease-induced hyperammonaemia

Abstract

The capillary diameter, the capillary area as percentage of brain area, the minimal intercapillary distance, the harmonic mean basement membrane thickness and the mitochondrial content of capillar endothelium were estimated in the striatum of normal rats and after 4 days'' ureaseinduced hyperammonemia. Electronic image analysis, planimetry and classification with a ruler were used. The capillary diameter was increased after 4 days'' hyperammonemia. The mitochondrial content of capillary endothelium was decreased after hyperammonemia; all other parameters were unchanged. Using an inverse log transformation, the distribution of the basement membrane intercepts was approximately normal. The increased capillary diameter may result from vascular paralysis induced by hyperammonemia. The metabolic working capability is decreased in hyperammonemia, but the diffusion properties across the basement membrane and in the brain parenchyma appear morphologically unchanged.