Regulation of lactic acid production during exercise

Cortisol has minimal effects on lung maturation in fetal sheep before 130 days gestation. To test whether there is enhancement of cortisol action by other hormones, cortisol (F), triiodothyronine (T3), epinephrine (E), prolactin (PRL), and epidermal growth factor (EGF), alone or in combination, were infused into fetal sheep for 84 h between 124 and 128 days gestation. A mixture of F + T3 + PRL, but not any combination of two hormones, increased both distensibility [1.71 +/- 0.12 (SE) ml of air/g wet wt at 40 cmH2O, V40] and stability (1.16 +/- 0.09 ml of air per g wet wt at 5 cmH2O, V5) to near full-term values, above values resulting from treatment with F alone (0.91 +/- 0.12 and 0.43 +/- 0.09 ml/g, P less than 0.01). Only F had an effect when given alone, V40 increasing (P less than 0.05). Treatment with F + T3 (0.81 +/- 0.18 ml/g) and F + E (0.77 +/- 0.07 ml/g) increased V5 above values obtained with F alone (P less than 0.05). Alveolar saturated phosphatidylcholine (SPC) was higher after treatment with F + T3 (161 +/- 52 micrograms/g), F + T3 + PRL (156 +/- 53 micrograms/g, P less than 0.05), and F + E (113 +/- 40 micrograms/g, P = 0.07) than after F (12 +/- 3 micrograms/g). We conclude that F, T3, and PRL have a synergistic effect on the development of distensibility and stability of the ovine fetal lung.