title: Regulation of cutaneous gas exchange by environmental O2 and CO2 in the frog.
abstract: The effects of environmental PO2 and PCO2 on cutaneous blood flow and gas exchange were investigated in the frog, Rana pipiens. Halothane (Ha) anesthetized frogs were equilibrated with 9.5% Freon-22 (Fr), 1.1% Ha and air while placed in a box. A gas mixture, initially free of Ha and Fr, was drawn through a small test chamber placed on the abdomen. The excretion of Fr, Ha and CO2 into the sample chamber was analyzed by a mass spectrometer. Under these conditions, changes in Fr or Ha excretion into the sample chamber reflected local changes in skin perfusion. Raising sample chamber [O2] produced concentration-dependent increases in the excretion of all gases measured. Lowering chamber [O2] reduced gas excretion. Increasing chamber [CO2] to 5% decreased the excretion of Fr and Ha. Increasing box [O2] to 86.5% while keeping sample chamber [O2] constant at 21% decreased gas excretion into the chamber. Selectively raising box [CO2] to 4.3% increased gas excretion into the chamber. The results indicate that regional cutaneous blood flow and gas exchange is a direct function of the [O2] directly above that portion of skin, and inversely related to the [O2] over adjacent skin. This regional perfusion-O2 matching may act to optimize total cutaneous gas exchange in the frog. In addition, CO2 may be an important regulator of cutaneous blood flow distribution.
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000502:physiology*; D005617:Chlorofluorocarbons, Methane; D006221:Halothane; D010100:Oxygen / Q000502:physiology*; D011894:Rana pipiens / Q000502:physiology*; D012039:Regional Blood Flow; D012119:Respiration; D012867:Skin / Q000098:blood supply*; D012879:Skin Physiological Phenomena
chemical_list: D005617:Chlorofluorocarbons, Methane; D002245:Carbon Dioxide; D010100:Oxygen; D006221:Halothane