title: Physiology of hibernation in Rana pipiens: metabolic rate, critical oxygen tension, and the effects of hypoxia on several plasma variables.
abstract: Rates of O(2) consumption (.VO(2)) were determined for adult northern leopard frogs (Rana pipiens) submerged at 3 degrees C at water PO(2)s (P(w)O(2)) ranging from 0-160 mmHg. The critical O(2) tension (P(c)) was 36.4 mmHg. Hematocrit and blood levels of PO(2), glucose, lactate, pH, [Na(+)], [K(+)], and osmolality were determined for frogs submerged for two days. Above a P(w)O(2) of 50 mmHg, blood PO(2) ranged from 1-7 mmHg, which was sufficient to allow the frogs to function entirely aerobically. Plasma [lactate] increased as P(w)O(2) fell below 50 mmHg, the increase preceding significant changes in any other variable, and apparently preceding a fall in .VO(2). Most other variables showed little or no change from those of air-breathing control animals, even during anoxia. We present an analysis of the importance of a large decrease in P(c) in permitting frogs to successfully overwinter in icebound ponds and of the factors that contribute to that decrease.
authors.affiliation: Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA. gultsch@biology.as.ua.edu
authors.forename: Gordon R
authors.initials: GR
authors.lastname: Ultsch
authors.forename: Scott A
authors.initials: SA
authors.lastname: Reese
authors.forename: E Ray
authors.initials: ER
authors.lastname: Stewart
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose; D005618:Fresh Water; D006605:Hibernation / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood; D009994:Osmolar Concentration; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D011894:Rana pipiens / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D019344:Lactic Acid; D010100:Oxygen