Hypoxia during the perinatal period and during early infancy is a significant cause of mortality and morbidity. Adrenocortical hormones are a vital component of the adaptation to hypoxic stress. Furthermore, neonatal hypoxic hyperlipidemia is a significant clinical entity, and changes in specific lipid metabolites alter adrenal function. The long-term objective of this proposal is to characterize the short and long-term consequences of perinatal hypoxia on the control of the hypothalamic-pituitary-adrenal (HPA) system and lipid metabolism in the rat.
Specific Aims 1 and 2 will evaluate the effect of neonatal hypoxia on the control of the hypothalamic-pituitary-adrenal axis by evaluating intracellular and systemic controllers of steroidogenesis, the timing and mechanisms of the stress-hyporesponsive period (SHRP), and the negative feedback control of CRH and POMC expression and ACTH release.
Specific Aim 3 will characterize the long-term sequellae of perinatal hypoxia by evaluating subsequent HPA responses to stimuli in the adult rat.
Specific Aim 4 will more fully characterize neonatal hypoxic hyperlipidemia by analyzing the interaction of neonatal hypoxia and glucocorticoid therapy, and by performing metabolomic analysis. Neonatal hypoxia from birth is accomplished by exposing newborn rats (with their lactating dams) to a hypoxic environment. Perinatal hypoxia is accomplished by exposing late-gestational pregnant rats to hypoxia and allowing them to deliver in a hypoxic environment. Physiological, biochemical and molecular assessment of adrenocortical function is performed by ACTH injection in vivo, using dispersed cells, evaluating StAR and PBR expression, and measuring CBG and glucocorticoid clearance. Hypothalamic-pituitary function is assessed by measuring stress- and CRH-induced ACTH release, by evaluating feedback sensitivity, and by analyzing pituitary, hypothalamic, and hippocampal function and pertinent receptor/hormone expression. Metabolic function is assessed by analysis of hepatic enzyme activity, as well as complete metabolomic analysis of serum and hepatic lipids. Characterization of the hypothalamic-pituitary-adrenal and metabolic adaptations to perinatal hypoxia can lead to new diagnostic approaches and therapies to minimize morbidity and mortality.
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