Chronic hypoxia and the cerebral circulation.
Exposure to mild hypoxia elicits a characteristic cerebrovascular response in mammals, including humans. Initially, cerebral blood flow (CBF) increases as much as twofold. The blood flow increase is blunted somewhat by a decreasing arterial Pco2 as a result of the hypoxia-induced hyperventilatory response. After a few days, CBF begins to fall back toward baseline levels as the blood oxygen-carrying capacity is increasing due to increasing hemoglobin concentration and packed red cell volume as a result of erythropoietin upregulation. By the end of 2 wk of hypoxic exposure, brain capillary density has increased with resultant decreased intercapillary distances. The relative time courses of these changes suggest that they are adjusted by different control signals and mechanisms. The CBF response appears linked to the blood oxygen-carrying capacity, whereas the hypoxia-induced brain angiogenesis appears to be in response to tissue hypoxia.
Xu
Kui
K
Dept. of Anatomy, School of Medicine, Case Western Reserve Univ., 10900 Euclid Ave., Cleveland, OH 44106-4930, USA.
Lamanna
Joseph C
JC
D000818:Animals; D001810:Blood Volume; D001921:Brain / Q000098:blood supply* / Q000473:pathology / Q000503:physiopathology; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002908:Chronic Disease; D006801:Humans; D006985:Hyperventilation / Q000097:blood / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000473:pathology / Q000503:physiopathology*; D009389:Neovascularization, Pathologic; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D013045:Species Specificity; D013997:Time Factors
D002245:Carbon Dioxide; D010100:Oxygen