Autogenous vein grafts in hypertensive (SHRSR) rats have increased smooth muscle cell hyperplasia in the graft neo-intima, compared with grafts in normotensive rats.

This study examined the effects of raised intralumenal blood pressure on smooth muscle cell hyperplasia in the neo-intimal layer of experimental vein-to-artery grafts in rats. Autogenous vein grafts 1 mm in diameter and 4 mm long were inserted microsurgically into the left common iliac arteries of 24 genetically hypertensive (SHRSR) rats. At 2, 4, 6, 12, and 26 weeks after insertion, the grafts and contralateral unoperated iliac arteries were perfused at constant pressure and removed for histological and morphometric analyses. Neo-intimal thicknesses of the grafts and the intima-plus-media thicknesses of the contralateral arteries in the same rats were measured and compared statistically. From previous studies it is clear than in normotensive rats the neo-intima stabilises once it reaches the equivalent thickness of the contralateral arterial intima-plus-media, about 4 weeks after graft insertion. In the SHRSR rats the graft neo-intima developed at a similar rate (over the first 4 weeks) to that seen in previous studies in normotensive rats, but the development continued to occur over a longer period (6 weeks); therefore the neo-intima became significantly thicker. The graft neo-intima in SHRSR rats also became much thicker than the functionally equivalent intima-plus-media of the contralateral unoperated iliac arteries in the same rats. It was hypothesised that higher intralumenal blood pressure to SHRSR rats stimulates neo-intimal hyperplasia, resulting in the development of a thicker graft neo-intima, compared with that in normotensive rats.