Mechanisms of Interaction of Albumin with Arterial Elastin

Binding of proteins, lipoproteins and calcium salts to arterial elastin occurs with age and in disease. In order to clarify the mechanisms of interaction we investigated the binding of native and charge-modified albumins to elastin isolated by alkali extraction of the porcine aorta. Fluorescence microscopy was used to quantify the distribution of lissamine-rhodamine labelled albumins in native and charge-modified elastins under different solution conditions. For native albumin uptake was approximately twice as high on the intimal and adventitial sides as in the mid media. The distribution of anionic albumin was very similar, but methylation either of the albumin or the elastin greatly reduced the transmural variation. The uptake of methylated albumin was approximately three-fold greater than the native albumin. The uptake of the native albumin was reduced preferentially in the intimal region in the presence of calcium and only the charge-modified proteins were able to penetrate the intralamellar space. These observations demonstrated the importance of hydrophobic interactions in albumin binding.