Total and active ghrelin in developing rats during hypoxia.

Hypoxia is well known to decrease appetite and weight gain in growing rats, and to induce weight loss in humans. It has been hypothesized that this is mediated by a change in ghrelin, an orexigenic peptide synthesized and released primarily from the stomach. Rats were exposed to hypoxia for 7 d as neonates (birth-7 d of age), weanlings (28-35 d of age), and juveniles (49-56 d of age). Hypoxia had no effect on total or active plasma ghrelin. There was a significant decrease in active ghrelin in weaned rats (0.8 +/- 0.1 ng/mL) compared to nursing pups at 7 d of age (2.3 +/- 0.2 ng/mL). The proportion of total ghrelin that was active decreased significantly between 7 and 35 d of age. We conclude that the anorexia and weight loss associated with hypoxia is probably not mediated by ghrelin. There appear to be changes in active ghrelin levels in plasma during early development in the rat.