Chemoreflex contribution to adrenocortical function during acute hypoxemia in the llama fetus at 0.6 to 0.7 of gestation.
This study tested the hypothesis that the fetal llama, a species adapted to the chronic hypoxia of life at high altitude, demonstrates a potent carotid chemoreflex influence on adrenocortical responses during acute hypoxemia. Plasma ACTH and cortisol concentrations, and mesencephalic and adrenal blood flows were measured during a 1-h period of acute hypoxemia in six intact and four carotid sinus-denervated llama fetuses at 0.6-0.7 of gestation. Fetal PaO2 was reduced from approximately 23 to about 14 mm Hg in both intact and carotid-denervated groups during acute hypoxemia. During hypoxemia, fetal plasma ACTH, adrenal blood flow, and, therefore, delivery of ACTH to the adrenals increased to similar extents in both intact and carotid-denervated fetal llamas. Despite this, the increase in plasma cortisol in hypoxemia in intact fetuses was absent in carotid-denervated fetuses. In addition, the increase in delivery of cortisol to the mesencephalon calculated in intact fetuses during hypoxemia did not occur in the carotid-denervated group. These data suggest that the integrity of the carotid chemoreceptors is indispensable to cortisol release during acute hypoxemia in the llama fetus, even at 0.6-0.7 of gestation.
Riquelme
R A
RA
Campus Oriente, Instituto de Ciencias Biomédicas, Facultad de Medicina, International Center for Andean Research, Universidad de Chile, Santiago.
Llanos
J A
JA
McGarrigle
H H
HH
Sanhueza
E M
EM
Hanson
M A
MA
Giussani
D A
DA
D000302:Adrenal Cortex / Q000098:blood supply / Q000196:embryology* / Q000503:physiopathology; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000531:Altitude; D000818:Animals; D001794:Blood Pressure; D002161:Camelids, New World / Q000196:embryology*; D002245:Carbon Dioxide / Q000097:blood; D002339:Carotid Arteries / Q000503:physiopathology; D002628:Chemoreceptor Cells / Q000502:physiology*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006454:Hemoglobins / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology*; D008636:Mesencephalon / Q000098:blood supply; D010100:Oxygen / Q000097:blood; D011247:Pregnancy
D006454:Hemoglobins; D002245:Carbon Dioxide; D000324:Adrenocorticotropic Hormone; D010100:Oxygen; D006854:Hydrocortisone