title: Carotid bodies are required for ventilatory acclimatization to chronic hypoxia.
abstract: We have compared the ventilatory responses of intact and carotid body-denervated (CBD) goats to moderate [partial pressure of O2 in arterial blood; (Pao2) approximately 44 Torr] and severe (Pao2 approximately 33 Torr) many time points for up to 7 days of hypobaria. In the intact group there were significant time-dependent decreases in partial pressure of CO2 in arterial blood (PaCO2) in both moderate and severe hypoxemia (approximately-7 and -11 Torr) that were largely complete by 8 h of hypoxemia and maintained throughout. Acute restoration of normoxia in chronically hypoxic intact animals produced time-dependent increases in Paco2 over 2 h, but hypocapnia persisted relative to sea-level control. Arterial plasma [HCO3-] and [H+] decreased, and [Cl-] increased with a time course and magnitude consistent with developing hypocapnia. Chronic CBD, per se, resulted in a sustained, partially compensated respiratory acidosis, as PaCO2 rose 6 Torr and base excess rose 3 mEq/1, [Cl-] fell 1 mEq/1, and pHa fell 0.01 units. During exposure to identical levels of arterial hypoxemia as in the intact group. CBD animals showed no significant changes in PaCO2, [H+]a, or [HCO3-]a at any time during moderate or severe hypoxemia. Plasma [C1-] remained within the normal range throughout exposure to moderate hypoxia and increased in severe hypoxia. In a few instances some hypocapnia was observed, but this was highly inconsistent and was always less than one-third of that observed in intact goats. In contrast to intact goats, acute restorations of normoxia in the chronically hypoxic CBD goats always caused hyperventilation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.forename: C A
authors.initials: CA
authors.lastname: Smith
authors.forename: G E
authors.initials: GE
authors.lastname: Bisgard
authors.forename: A M
authors.initials: AM
authors.lastname: Nielsen
authors.forename: L
authors.initials: L
authors.lastname: Daristotle
authors.forename: N A
authors.initials: NA
authors.lastname: Kressin
authors.forename: H V
authors.initials: HV
authors.lastname: Forster
authors.forename: J A
authors.initials: JA
authors.lastname: Dempsey
mesh_terms: D000064:Acclimatization; D000136:Acid-Base Equilibrium; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002344:Carotid Body / Q000502:physiology*; D003714:Denervation; D000860:Hypoxia / Q000503:physiopathology; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000378:metabolism; D012119:Respiration
chemical_list: D002245:Carbon Dioxide