Corticotropin and cortisol responses to corticotropin-releasing factor in the chronically hypoxemic ovine fetus

OBJECTIVE: The purpose of this study was to determine if mild hypoxemia (~ 25% below normal) of at least 5 days' duration alters corticotropin and cortisol responses to corticotropin-releasing factor. STUDY DESIGN: We studied 14 (hypoxemic, n = 5; normoxemic, n = 9) fetuses of 135 ± 1 (mean ± SEM) days' gestational age. Fetuses were placed in the experimental group if arterial Po2 was ≤ 16 mm Hg for 5 days. In normoxemic animals arterial Po2 was ≥ 17 mm Hg. Plasma hormone responses were compared by analysis of variance. RESULTS: Resting corticotropin levels were not different (hypoxemic 26 ± 5 pg/ml, normoxemic 29 ± 12 pg/ml), and corticotropin-releasing factor (530 ± 30 ng/kg) increased (p = 0.01) corticotropin levels similarly in both groups. Basal plasma cortisol levels (hypoxemic 20 ± 10 ng/ml, normoxemic, 30 ± 7 ng/ml) were not significantly different. Both groups had similarly increased (p \lt 0.01) plasma cortisol levels after corticotropin-releasing factor administration. CONCLUSION: Mild hypoxemia lasting 5 days does not significantly alter corticotropin and cortisol responses to corticotropin-releasing factor in the late-gestation ovine fetus. (AM J OBSTET GYNECOL 1992;167:1686-90.)