Objective: Endothelin (ET) has, since its discovery, increasingly been considered a key player in the pathophysiological processes of cerebral vasospasm in the course of subarachnoid hemorrhage, although it remains unclear how ET is involved. We present data that indicate an inherent capacity of human cerebral arteries to change their sensitivity to ET.
Methods: Human cerebral arteries were obtained from patients undergoing intracranial tumor surgery. The vessels were divided into segments and subjected to organ culture for 48 hours. The vessels were then examined by using in vitro pharmacological methods and molecular biological techniques.
Results: After organ culture of the cerebral arteries, both the sensitivity to and potency of ET were enhanced (maximal response, 152 +/- 9%; -log (50% effective concentration), 10.3 +/- 0.3), in comparison with data for fresh cerebral arteries. Contractions were inhibited by both FR139317 (a specific ET(A) receptor antagonist) and bosentan (a mixed ET(A) and ET(B) receptor antagonist), in a manner indicating the sole presence of contractile ET(A) receptors. An inconsistent dilative response to the selective ET(B) receptor agonist sarafotoxin 6c was observed; the response was preserved in some segments and abolished in others, and potentiation of the precontraction was observed in yet other segments. No isolated contractile response to sarafotoxin 6c was observed, however. In reverse transcription-polymerase chain reaction assays, both ET(A) and ET(B) receptor messenger ribonucleic acid was detected.
Conclusion: These results demonstrate that human cerebral arteries are capable of enhancing the function of ET(A) receptors.