Microarray and real-time PCR analysis of adrenal gland gene expression in the 7-day-old rat: effects of hypoxia from birth

Abstract

Bruder ED, Lee JJ, Widmaier EP, Raff H. Microarray and real-time PCR analysis of adrenal gland gene expression in the 7-day-old rat: effects of hypoxia from birth. Physiol Genomics 29: 193-200, 2007. First published January 9, 2007; doi:10.1152/physiolgenomics.00245.2006.-We hypothesize that changes in adrenal gene expression mediate the increased plasma corticosterone and steroidogenesis in rat pups exposed to hypoxia from birth. In the current study, rat pups (with their dams) were exposed to hypoxia from birth and compared with pups from normoxic dams fed ad libitum or pair fed to match the decreased maternal food intake that occurs during hypoxia. Microarray analysis was performed, followed by verification with real-time PCR. Furthermore, the expression of selected genes involved in adrenal function was analyzed by real-time PCR, regardless of microarray results. Hypoxia increased plasma ACTH and corticosterone, while food restriction had no effect. Microarray revealed that many of the genes affected by hypoxia encode proteins that require molecular oxygen (monooxygenases, oxidoreductases, and electron transport), whereas only a few genes known to be involved in adrenal steroidogenesis were affected. Interestingly, the expression of genes involved in mitochondrial function and intermediary metabolism was increased by hypoxia. Real-time PCR detected a small but significant increase in the expression of Cyp21a1 mRNA in the hypoxic adrenal. When decreased maternal food intake was controlled for, the effects of hypoxia were more pronounced, in that real-time PCR detected significant increases in the expression of Star (244%), Cyp21a1 (208%), and Ldlr (233%). The present study revealed that increased plasma corticosterone in rat pups was due to hypoxia per se, and not as a result of decreased food intake by the hypoxic dam. Furthermore, hypoxia induced changes in gene expression that account for more productive and efficient steroidogenesis. steroidogenesis; neonatal; mRNA; adrenal cortex; corticosterone; ACTH SYSTEMIC HYPOXIA IS A CONDITION frequently encountered in the neonatal intensive care unit, is often a complication of preterm birth, and is associated with significant morbidity and mortality (9, 19). The ability to survive a hypoxic episode depends on coordinated physiological responses by a number of systems. These responses include, but are not limited to, adaptations in metabolic, hemodynamic, digestive, and cardiorespiratory function (8,10,13,17,22). A coordinated endocrine response is also a critical component (23,26). The ability of the neonatal hypothalamic-pituitary-adrenal (HPA) axis to mount a response to low oxygen is of paramount importance. A majority of preterm infants lack the capacity for an adrenocortical response to exogenous ACTH and physiological stressors, and this leads to enhanced inflammation and decreased pulmonary function requiring ventilation (15, 35).In the neonatal rat, there is a unique developmental aspect to the maturation of the adrenocortical response to stressors such a...

Epidermal Growth Factor and Parathyroid Hormone-related Peptide mRNA in the Mammary Gland and their Concentrations in Milk: Effects of Postpartum Hypoxia in Lactating Rats

“…Hypoxia from parturition to PD7 significantly decreased maternal body weight (from 281 ±4g to 247±5g; p<0.001). The hypoxia-induced decrease in maternal body weight coincided with the decrease in food intake that we previously reported [7]. Based on these observations, normoxic dams (with their litters) were pair fed according to hypoxic dam intake.…”

“…Litter size was normalized to 12 pups per litter (mixed sexes). Maternal food intake was measured in normoxic and hypoxic dams as described previously [7]. The amount of food equivalent to the average daily intake of the hypoxic dams was then given to a separate set of normoxic dams (pair-fed group; n = 9).…”

“…This adaptation may modulate neonatal small intestinal enzyme activity, which we have demonstrated previously [35]. Because we have also shown that hypoxia lowers maternal food intake [7], we studied normoxic dams that were fed ad libitum and normoxic dams that were pair fed to account for the effects of decreased caloric intake per se on milk composition. Maternal body weight and mammary gene expression were measured as part of this initial investigation.…”

“…Alterations in maternal food intake may have profound effects on the development of the neonate via changes in milk composition and/or production [4][5][6]. Systemic hypoxia modulates a number of physiological systems and has significant effects on food intake [7][8][9][10][11][12][13][14]. In addition, chronic hypoxia during lactation may affect the composition of expressed milk via alterations in maternal metabolism and mammary gland physiology [15][16][17].…”

Nicotinamide Mononucleotide Adenylyltransferase Is a Stress Response Protein Regulated by the Heat Shock Factor/Hypoxia-inducible Factor 1α Pathway

“…For example, treating parental salt-sensitive rats with mild hypoxia (12% oxygen) revealed a 1.96-fold up-regulation of NMNAT1 transcripts (p Ͻ 0.0005) (48), and treating the quadriceps of mice in hypoxic conditions for 2 weeks induced a 2.23-fold up-regulation of NMNAT1 transcript levels (p Ͻ 0.0079) (49). In Saccharomyces cerevisiae, a 45-min exposure to anoxic conditions induced a robust up-regulation of NMNAT transcription (fold change, 1.8; p Ͻ 0.04) (50).…”