Proliferation of smooth muscle cells in the thoracic aorta after injury to the abdominal aorta: evidence for a humoral mediator in experimental arteriosclerosis.

We tested the hypothesis that circulating humoral material(s) can induce vascular smooth muscle cells to synthesize DNA and to proliferate. Either the entire aorta or its abdominal segment was balloon de-endothelialized in four groups of rabbits. In the first group (control), the entire aorta was injured, and no further procedures were carried out. In a second group (reinjury), the abdominal aortic segment was reinjured 4 days after the initial de-endothelialization procedure. A third group (sham) had a second sham operation 4 days after initial injury. In a fourth group (abdominal only), the abdominal aortic segment was injured on two occasions 4 days apart. There was a rise in the specific activity of 3H-thymidine incorporation into smooth muscle cell DNA (DNA-SA) of the thoracic segments, which began 12 hours after reinjury, peaked within 24 hours at 335 +/- 63 dpm/micrograms DNA (+/- SEM), and returned to control level within 72 hours. The DNA-SA of the thoracic aorta of control rabbits and sham-operated animals 4.5 days after the initial injury was 86 +/- 19 and 48 +/- 8 dpm/micrograms DNA, respectively. There was no rise in DNA-SA in the thoracic aorta of animals in which the abdominal aorta was injured twice. Intimal cell nuclei per 0.1 mm internal elastic lamina were counted 3 days after the second injury and showed similar differences between doubly injured and control animals. Platelet accumulation, as measured by chromium 51 platelet attachment to the aortic surface, was increased in the abdominal segment 12 hours after reinjury.(ABSTRACT TRUNCATED AT 250 WORDS)