The mitochondrial content of endothelial cells and the basement membrane thickness of rat brain capillaries after portocaval anastomosis.

The volume of mitochondria in brain capillary endothelium and the harmonic mean basement membrane thickness were estimated in rats after protocaval anastomosis for 10 days, 30 days and 10 weeks. The mitochondrial volume was from 5.73% to 7.64% of the endothelial volume. There was no difference between the control and experimental animals. The harmonic mean thickness of the basement membrane was calculated from orthogonal intercepts measured on a reciprocal logarithmic scale. This method leads to an approximately normal distribution of the measurements. The harmonic mean thickness was 57.8 nm in controls, 54.6 nm after 10 days, 63.2 nm after 30 days and 60.0 nm after 10 weeks portocaval anastomosis. The increase after 30 days was significantly different from the first two measurements. It is concluded that only a small increase in harmonic mean thickness of the basement membrane, and thereby an increase in diffusion resistance, have occurred after 30 days portocaval anastomosis.