Changes in the caldesmon isoform content and intimal thickening in the rabbit carotid artery induced by a silicone elastomer collar.

The presence of a silicone elastomer collar around one carotid artery of a rabbit induces thickening of the tunica intima. We used immunoblotting to study quantitatively changes in the isoforms of caldesmon, a protein implicated in the regulation of contractility in smooth muscle, while also monitoring the histological changes during 28 days after collaring. Control rabbit carotid arteries (n = 28) contained 245 +/- 6.4 nmol/g protein of the larger isoform of caldesmon (CDh) and 68.3 +/- 3.6 nmol/g protein of the smaller isoform (CD1). Four days after collaring, intimal thickening was slight, but 44% of arterial CDh had been lost; this loss of CDh was therefore from the tunica media. At 10 days, CDh fell to 37% of the control level. Immunofluorescence using CDh-specific antibodies showed that the CDh level was diminished but remained uniform across the wall of collared arteries. At 14 days, when intimal thickening was maximal, there was 30% more CD1 than in controls. At 28 days, the neointima had thinned, and CD1 had fallen to below control levels. Thus, CD1 levels reflected the development and regression of neointima. Changes in caldesmon isoforms showed that smooth muscle cell phenotypic changes occurred throughout the arterial wall.