Background—Beta-2 adrenoceptor agonists have been associated with sudden death in asthma patients but the cause and underlying mechanism are unclear. Animal experiments indicate that the combination of hypoxia and â2 agonists may result in detrimental cardiovascular effects. A study was undertaken to investigate the eVect of hypoxia on the systemic vascular eVects of salbutamol in patients with...

RATIONALE High-altitude pulmonary edema (HAPE) is characterized by excessive pulmonary vasoconstriction and is associated with decreased concentrations of nitric oxide (NO) in the lung. OBJECTIVES We hypothesized that individuals susceptible to HAPE (HAPE-S) would also have dysfunction of the vascular NO vasodilator pathway during hypoxia in the systemic vasculature. METHODS During normoxia...

Systemic hypoxia stimulates the release of vasopressin (VP) and adrenocorticotropin hormone (ACTH). To examine the involvement of catecholamine cell groups of the ventrolateral medulla (VLM) in the neuroendocrine responses, we have used the c-fos activity mapping technique to compare the effects of hypoxia on VLM catecholamine cells to those on neurosecretory VP and putative corticotropin relea...

Fletcher, Eugene C. Invited Review: Physiological consequences of intermittent hypoxia: systemic blood pressure. J Appl Physiol 90: 1600–1605, 2001.—One of the major manifestations of obstructive sleep apnea is profound and repeated hypoxia during sleep. Acute hypoxia leads to stimulation of the peripheral chemoreceptors, which in turn increases sympathetic outflow, acutely increasing blood pre...

In humans, the net effect of acute systemic hypoxia in quiescent skeletal muscle is vasodilation despite significant reflex increases in muscle sympathetic vasoconstrictor nerve activity. This vasodilation increases tissue perfusion and oxygen delivery to maintain tissue oxygen consumption. Although several mechanisms may be involved, we recently tested the roles of two endothelial-derived subs...

Targeted disruption of the gene for natriuretic peptide receptor-A (NPR-A) worsens pulmonary hypertension and right ventricular hypertrophy during hypoxia, but its effect on left ventricular mass and systemic pressures is not known. We examined the effect of 3 wk of hypobaric hypoxia (0.5 atm) on right and left ventricular pressure and mass in mice with 2 (wild type), 1, or 0 copies of Npr1, th...

Reductions in oxygen availability (O(2)) by either reduced arterial O(2) content or reduced perfusion pressure can have profound influences on the circulation, including vasodilation in skeletal muscle vascular beds. The purpose of this review is to put into context the present evidence regarding mechanisms responsible for the local control of blood flow during acute systemic hypoxia and/or loc...