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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypoxia decreases plasma aldosterone in vivo without a decrease in PRA, angiotensin II (ANG II), ACTH, or cortisol. The present study evaluated whether this could be due to a direct, specific inhibitory effect on the zona glomerulosa related to the magnitude of the decrease in oxygen (O2). Bovine adrenocortical cells were dispersed with collagenase and studied in vitro within 48 h. Cells were stimulated for 2 h with ANG II (0.1-1000 nM) or (Bu)2cAMP (0.3-3 mM) under oxygen levels ranging from 0 to 100% O2 (PO2 from 66 +/- 4 to 561 +/- 46 torr) vs. a reference gas mixture (21% O2 PO2 approximately 140 torr). Exposure to 123 +/- 8, 110 +/- 12, 100 +/- 16, and 66 +/- 4 torr led to 27%, 30%, 40% and 70% inhibition, respectively, of 3 nM ANG II-stimulated aldosterone secretion as compared to 140 +/- 16 torr (reference). Exposure to hyperoxia (288 +/- 36 to 561 +/- 46 torr) led to a small (10%) increase in ANG II-stimulated aldosterone secretion which was not statistically significant. The P50 (half-maximal PO2) for aldosteronogenesis was approximately 95 torr. The results for other doses of ANG II and for cAMP were similar. The inhibitory effect of low O2 was reversed by returning the cells to reference conditions (140 +/- 16 torr). Cortisol secretion was not significantly affected by changes in oxygen tension. We conclude that small changes in O2 within the physiological range directly and specifically inhibit aldosteronogenesis in a dose-dependent manner with a P50 of approximately 95 torr. Inhibition of cAMP-stimulated aldosterone secretion suggests a postreceptor site of action. This direct, reversible, and specific effect on the zona glomerulosa of the adrenal cortex may account for the dissociation of renin and aldosterone during hypoxia in vivo.
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PMID:The effect of oxygen on aldosterone release from bovine adrenocortical cells in vitro: PO2 versus steroidogenesis. 216 17

Neuroendocrine responses were investigated in 8 male athletes before, during and after 60 min of bicycle ergometry at an intensity corresponding to 1.5 mmol/l blood lactate in an incremental bicycle test. Hyperoxic gas (HE: 100% O2), hypoxic gas (HO: 14% O2, 86% N2) or normoxic gas (NO) were inhaled continuously during exercise as well as for 30 min before and after. During exercise, prolactin (PRL) increased in HO while it did not change significantly in NO. Only HE induced a PRL increase (400%) during 30 min of rest before exercise. PRL decreased in HE during exercise but remained higher than in HO. Growth hormone (GH), ACTH and norepinephrine (NE) did not increase in a similar pattern during HE. In comparison to NO and HE, increase of NE, GH and ACTH was significantly higher in HO, NE declined significantly in HE before exercise. Our results demonstrate that only PRL is affected by acute exposure to hyperoxia. Changes in inhibition of the dopaminergic system might contribute to augmentation of PRL before exercise. The exact underlying mechanisms are yet unknown.
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PMID:Increased prolactin response to hyperoxia at rest and during endurance exercise. 885 13

The synthesis of adrenal steroids requires molecular oxygen. Because arterial hypoxemia is a common clinical condition, the purpose of the present study was to examine steroidogenesis in vitro under physiological changes in O(2) tension (Po(2)) in cells from human adrenal glands with aldosterone-secreting adenomas (ASA; n=3) or with bilateral adrenal hyperplasia causing Cushing's syndrome (n=4). A decrease in Po(2) from 150 mmHg (mild hyperoxia) to 80 mmHg had minimal effect on steroid production. A reduction to 40 mmHg (still well within the physiological range) significantly inhibited cAMP- and ACTH-stimulated aldosterone, cortisol, and dehydroepiandrosterone (DHEA) production from ASA. Furthermore, cortisol and DHEA production in cells from histologically normal tissue, adjacent to ASA and from bilateral adrenal hyperplasias, was also inhibited under a Po(2) of 40 mmHg. We conclude that physiological decreases in Po(2) to levels typical for adrenal venous Po(2) under mild hypoxia inhibit steroidogenesis. These studies may have implications for oxygen therapy in critically ill patients with functional adrenal insufficiency, as well as for therapeutic options in patients with adrenal neoplasms.
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PMID:Steroidogenesis in human aldosterone-secreting adenomas and adrenal hyperplasias: effects of hypoxia in vitro. 1610 60