Abstract

We report a method to determine the chemical composition of the first few layers of molecules making up the intimal surface of the bovine aorta. We gently and uniformly spray-abrade the opened, flat surface of the aorta with fine, dry potassium bromide (KBr) powder. Surface molecules are rubbed off and collected with the KBr powder. This powder is pressed into a disk and analyzed by infrared spectroscopy. The thickness of the surface sample is estimated from the density-mass-volume (area times thickness) relationship. We designed and constructed a mechanical spray abrader to analyze blood vessel surfaces. The uniformity and depth of abrasion are controlled by the angle of spray, pressure, distance, and rate of traverse of sample drum. Several successive surface samples may be removed from one blood vessel. In complementary work, a method was developed for the physical removal and mounting of the intima of arteries and veins as intact films for infrared analysis. Preliminary experiments on bovine aortas gave surface samples as thin as 57 Å (estimated) and with an infrared spectrum markedly different from that of the total aortic intimal film. The major infrared bands found in the surface samples were: NH (3300 cm⁻¹); CH (lipid) (2920 cm⁻¹); amides I and II (1650 and 1540 cm⁻¹); and, as a tentative assignment, sulfate (1050 cm⁻¹). Comparison of surface spectra with intimal film spectra suggests that the surface protein is different from intimal protein. The surface spectra resemble chondroitin sulfate, but not heparin. Possibly the first few molecular layers of intimal surface contain chondroitin sulfate. These methods may prove to be of value in determining the role of the intima and intimal surface in cardiovascular disease.

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