High altitude-induced changes in q-adrenergic receptors and Ins ( l,4,5)P3 responses in cerebral arteries

receptors and Ins ( 1,4,5)P3 responses in cerebral arteries. Am. J. Physiol. 272 (Regulatory Integrative Comp. Physiol. 41): R669-R674, 1997.-In response to high-altitude long-term hypoxemia, the cerebral arteries of fetal and adult sheep show decreased contractile responses to norepinephrine (NE) and other agonists. To test the hypothesis that hypoxia-induced developmental and vessel specific cerebral artery contractility changes are mediated, in part, by changes in ai-adrenergic receptor (al-AR) density and/or NE-induced inositol 1,4,5trisphosphate [Ins ( 1,4,5)P3] responses, we per-formed the following study. In common carotid (Corn) and main branch cerebral (MBC) arteries from normoxic adult ewes and near-term fetuses and those acclimatized to high altitude (3,820 m), we quantified OI~-AR density (maximal binding in fmoVmg protein) and affinity (dissociation con