Population dynamics of arterial cells during atherogenesis. XIII. Mitogenic and cytotoxic effects of a hyperlipidemic (HL) diet on cells in advanced lesions in the abdominal aortas of swine fed an HL diet for 270-345 days.

The abdominal aortas of five groups of young male Yorkshire swine were studied: (1) 0-day baseline group; (2) hyperlipidemic (HL) group with ballooning; (3) mash group with ballooning; (4) mash group without ballooning; and (5) HL group without ballooning. The last four groups were injected with [3H]thymidine at 270 days and sacrificed subsequently in subsets at intervals up to 75 days in order to study births and deaths (or loss by migration) among cells over the period 270-345 days. However, only in the HL-ballooned group were there enough swine for the isotopic data to be useful for most purposes. In the 0-day baseline group there were 6 +/- 2 X 10(6) cells in intimal cell masses (ICM); in the 270- to 345-day mash group without ballooning the number was 10 +/- 2 X 10(6), which is not a statistically significant increase over 0-day. This supports the hypothesis that in the normal state births and deaths (or loss by migration) among cells in ICM are nearly balanced at least up to 1 year of age. In the 270- to 345-day mash group with ballooning there were 61 +/- 12 X 10(6) cells in the ICM. Thus a single episode of deendothelialization results in tremendous hyperplasia of ICM. However, even the largest ICM (atherosclerotic lesion) in this group showed essentially no necrosis. In the 270- to 345-day HL group with ballooning there were 108 +/- 17 X 10(6) cells in the ICM turned atherosclerotic lesions. In addition an average of one-third of the lesion volume was occupied by lipid-rich, calcific necrotic debris. Thus the HL diet appears to have associated with it both mitogenic and cytotoxic influences on ICM cells. In the 270- to 345-day HL group not ballooned there were 130 +/- 30 X 10(6) lesion cells and lesions were somewhat more extensive and necrotic than in the HL-ballooned group, probably because the former group included by chance more hyperresponders (as regards serum cholesterol values) to the HL diet than the latter. Regardless of this, the data suggest that in this particular model of advanced atherosclerosis the balloon-injury stimulus to proliferation and the HL-diet stimulus are neither additive nor synergistic.(ABSTRACT TRUNCATED AT 400 WORDS)