Ventilatory chemosensitivity and thermogenesis of the chicken hatchling after embryonic hypercapnia.
Hypoxia during incubation results in hatchlings with a reduced thermogenic capacity and a blunted ventilatory (V (E)) chemosensitivity (Szdzuy, K., Mortola, J.P., 2007b. Ventilatory chemosensitivity of the 1-day-old chicken hatchling after embryonic hypoxia. Am. J. Physiol. (Regul. Integr. Comp. Physiol.) 293, R1640-R1649). We asked if similar effects occurred with embryonic hypercapnia, that is, with a non-hypoxic sustained stimulation of the chemoreceptors. White Leghorn chicken eggs were incubated at 38 degrees C either in air (controls, C) or in 4% CO(2) from embryonic day 5 (4% CO(2)), hatching included. The 4% CO(2) embryos hatched about 12h later than C, with similar body weight. On the day of hatching the thermogenic capacity, assessed from the changes in oxygen consumption (.V(O2)) during 1h at 30 degrees C, increased from the early (about 3h old) to the late hours (about 20 h old), and was similar between 4% CO(2) and C. Ventilatory chemosensitivity was evaluated from the changes in (.V(E)) and in ventilatory equivalent (.V(E)/.V(O2)) during acute hypoxia (15 and 10% O(2), 20 min each) or hypercapnia (2 and 4% CO(2), 20 min each). Both at the early and late hours (.V(E)) chemosensitivity was lower in 4% CO(2) than in C. The .V(E)/.V(O2) responses of 4% CO(2) in hypoxia and hypercapnia averaged, respectively, about 45 and 60% of C. A separate set of eggs incubated in 2% CO(2) gave results qualitatively intermediate between C and 4% CO(2). We conclude that prenatal hypercapnia does not compromise the newborn's thermogenesis, but, like hypoxia, affects the development of respiratory control, resulting in a blunted chemosensitivity.
Szdzuy
Kirsten
K
Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada.
Mortola
Jacopo P
JP
D000818:Animals; D002628:Chemoreceptor Cells / Q000502:physiology*; D002642:Chick Embryo; D003080:Cold Temperature; D006935:Hypercapnia / Q000503:physiopathology; D000860:Hypoxia / Q000196:embryology*; D010101:Oxygen Consumption / Q000502:physiology; D012123:Pulmonary Ventilation; D012119:Respiration; D022722:Thermogenesis; D013990:Tidal Volume; D013997:Time Factors