Protein Synthesis and Immunoreactivities of Contraction-Related Proteins in Smooth Muscle Cells of Canine Basilar Artery after Experimental Subarachnoid Hemorrhage

Abstract

We examined time-dependent changes in protein synthesis and in the immunoreactivities of representative contraction-related structural proteins in smooth muscle cells of canine basilar arteries after experimental subarachnoid hemorrhage (SAH). Protein synthesis was assessed by the percentage of polyribosome-forming ribosomes to total ribosomes (aggregation rate), a morphological index of the activity of protein synthesis. The aggregation rates in prostaglandin F2α- (PGF2α) and 12- O-tetradecanoyl-phorbol-13-acetate (TPA)-induced contracted basilar arteries were 70.0 ± 7.0% and 71.4 ± 8.7%, respectively, quite similar to the value in normal basilar artery (73.0 ± 8.0%). In the single-SAH group with little delayed histological changes in the basilar arteries, the aggregation rate was significantly decreased to 30.5 ± 6.4% by 24 h after the SAH, and recovered to 52.3 ± 9.0% and 70.2 ± 7.6% at 7 and 14 days postSAH, respectively, when the vasospasm was moderately and completely ameliorated. In contrast, in the double-SAH group in which the basilar arteries developed delayed smooth muscle cell death and long-lasting arterial contraction, a significant decrease in the aggregation rate (25.0 ± 5.0% on day 4) persisted for 14 days. The in vitro incorporation of [3H]-leucine in the basilar arterial cells was also significantly suppressed 4 and 7 days after the initial SAH (1.2 ± 0.4 and 1.4 ± 0.3 × 103dpm/mg protein) in the double-SAH group, as opposed to no significant decrease in the basilar artery at 7 days postSAH in the single-SAH group (1.9 ± 0.6 × 103dpm/mg protein). The immunoreactivity of α-smooth muscle actin, a contractile protein, demonstrated by immunohistochemistry and immunoblots, was not altered for up to 14 days even in the double-SAH group, but that of calponin and of h-caldesmon, contraction-inhibiting proteins, was markedly reduced 4–14 days after the initial SAH. Persistent impairment of protein synthesis and relative reduction of immunoreactivities of the contraction-inhibiting proteins were observed in arteries with severe vasospasm and loss of smooth muscle cells, as noted in the double-SAH subjects. These abnormalities may cooperate to cause cerebral arterial narrowing accompanied by degeneration of smooth muscle cells after SAH.