No Effect of Bilirubin on Electrical Properties of Isolated Cerebrovascular Smooth Muscle Cells

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Abstract
An experimental model system, consisting of single isolated smooth muscle cells from the rat basilar artery, was developed to study the effects of spasmogens thought to play a role in the pathophysiology of cerebral vasospasm following subarachnoid hemorrhage. In this study, the effects of bilirubin and oxyhemoglobin were compared. Isolated cells were studied under phase contrast optics and with the whole-cell patch clamp technique. Cells exposed to saturated solutions of bilirubin for up to 11 h exhibited only a small degree of contraction which was not significantly different from that observed in similarly treated control cells. In contrast, oxyhemoglobin (1–10 µM) caused an increase in calcium-activated potassium currents, cell contraction, membrane blebbing and an irreversible and precipitous decline in membrane resistance within 5 min. While these experiments do not entirely rule out a role for bilirubin in cerebral vasospasm, they do suggest that oxyhemoglobin is much more likely to be important.

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