Experimental vasospasm in cultured arterial smooth-muscle cells. Part 1: Contractile and ultrastructural changes caused by oxyhemoglobin.

Smooth-muscle cells were cultured from rat aortic media, then oxyhemoglobin and other agents including serotonin, norepinephrine, and angiotensin II were added separately to the medium. Contractile and ultrastructural changes of the cells were examined with electron microscopy during the first 2 weeks of incubation. Oxyhemoglobin not only produced progressive contraction of the arterial smooth-muscle cells, but it also caused ultrastructural changes that resembled myonecrosis. In contrast, there was no evidence of progressive contraction or ultrastructural changes either in control cultures or in cultures with the other vasoactive agents. Although washout of oxyhemoglobin 3 hours after administration prevented continued contraction of the cells, washout 24 hours or longer after administration had no preventive effect. Judging from these results and from the fact that the culture medium was changed every 2 days, it is unlikely that accumulation of exogenous vasoactive agents caused these changes. The contraction and suggestive myonecrosis of the arterial smooth-muscle cells are probably caused by some intrinsic process initiated by oxyhemoglobin. The culture of cerebral arterial smooth-muscle cells requires further technical improvement; nevertheless, these results obtained with the smooth-muscle cells of rat aortic media indicate that arterial smooth-muscle cells in culture provide a promising new experimental model for chronic in vitro study of cerebral arterial spasm. It is suggested from these results that cerebral arteries are particularly prone to vasospasm because of structural differences as compared to noncerebral arteries.