Lack of correlation between adrenal cAMP and corticosteroidogenesis in the newborn rat.

In 2 to 16-day-old rats subjected to heat, the adrenal content of cAMP did not increase in animals younger than 14 days of age, but serum corticosterone was significantly higher than control values at all ages except in 10 and 12-day-old animals. This would suggest that cAMP may not mediate the adrenal steroidogenic response to stress during the first post-natal week. This hypothesis is consistent with the fact that the administration of 0.195 and 0.785 mU ACTH to 2-day-old rats resulted in a significant increase in serum corticosterone without a rise in the adrenal content of cAMP. The stress-induced rise in serum corticosterone progressively diminishes during the first post-natal week before returning to its previous 2-day-old capacity by day 16.