Investigations of fluorescent peptides and lipofuscins of human intervertebral disc relating to atherosclerosis.

(1) Annulus fibrosus and nucleus pulposus of human intervertebral discs at different degrees of atherosclerosis were disintegrated by elastase. (2) The material disintegrated by elastase -- called elastolysate -- could be separated into hydrophobic (apolar) and hydrophilic (polar) peptides. Parallel with the degree of atherosclerosis the amount of hydrophobic peptides increased, whereas that of the hydrophilic peptides decreased. (3) In annulus fibrosus and nucleus pulposus two kinds of fluorescence maxima were measured. The one, A:F 350:405, is known as fluorescence maxima of elastin- and collagen-peptides. The other, A:F 410:470, is related to a similar substance called atherofluorescent component (AFC), which has been isolated before from the plaques of atherosclerotic aorta. This substance accumulates mainly in nucleus pulposus and resembles lipofuscin-like bodies. (4) These bodies show a positive reaction with thiobarbituric acid, giving a red coloration characteristic for malondialdehyde. In nucleus pulposus the amount of lipofuscin-like substances is much greater than in annulus fibrosus. (5) The hydrophilic peptides, although they show the same fluorescence maxima as the hydrophobic peptides, do not give any reaction with thiobarbituric acid. It is supposed that in these cases the cross-linked protein contains instead of malondialdehyde other reactive aldehydes.