The internal elastic lamina in normal and abnormal human arteries. A barrier to the diffusion of macromolecules from the lumen.

The distribution of albumin in the walls of normal and abnormal human arteries from surgical and autopsy material was studied to gain insight into the barriers affecting the outward diffusion of plasma macromolecules. In normal arteries there was a steep reduction in albumin concentration at the position of the internal elastic lamina (IEL), suggesting that it acts as a barrier to diffusion. In abnormal arteries such as small vessels present in inflammatory tissue, the IEL was frequently discontinuous and associated with intimal thickening. In these small vessels reduplication of the IEL at the luminal margin of the thickened intima appeared to offer an effective new barrier to the diffusion of albumin from the lumen. In larger vessels such as the coronary arteries of adults, which invariably showed discontinuities of the IEL and intimal thickening, no such effective reduplicated IEL was present, and albumin diffused freely into the thickened intima. These observations suggest that the failure to form and maintain an IEL surrounding the arterial lumen may be associated with continued proliferation of intimal cells and progressive intimal thickening.