Hypoxia effects on hypothalamic corticotropin-releasing hormone and anterior pituitary cAMP.
OBJECTIVE
To study the effects of acute and chronic hypoxia on hypothalamus-anterior pituitary-adrenocortex axis.


METHODS
Rats and pikas were exposed to different altitude and periods. Animals were injected with CRH, Arg and NE in the third ventricle of the brain of rats.


RESULTS
Anterior pituitary cAMP and plasma corticosterone levels of rats obviously increased during 1 h of hypoxia. cAMP was increased from 2.23 +/- 0.13 of control group to 7.7 +/- 0.7 of 5 km and 13.4 +/- 1.9 nmol/g wet tissue of 8 km, respectively. i.c.v. CRH, Arg and NE all activated HPA axis. The effects of CRH were most potent. CRH 2 microL 0.75 nmol i.c.v increased anterior pituitary of cAMP from 3.5 +/- 0.4 of control to 22.4 +/- 2.2 nmol/kg wet tissue. Stimulating altitude of 5000 m resulted in a 16.9% decrease in corticosterone level (P < 0.05), 8000 m resulted in a 47.5% decrease (P < 0.01) after hypoxia for 25 d. Hypoxia did not activate HPA axis in pikas.


CONCLUSIONS
1) Hypoxia stress activates the secretion of corticotrophin (ACTH) via cAMP; 2) Adrenocotical function of rats decays during chronic hypoxia; 3) Arg and NE regulate the secretion of plasma corticosterone and synthesis of pituitary cAMP at the hypothalamus level; 4) Hypoxia tolerance of the pika was high.
Chen
Z
Z
Department of Animal Physiology, Northwest Plateau Institute of Biology, Chinese Academy of Sciences, Xining, China.
Du
J Z
JZ
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D005260:Female; D000860:Hypoxia / Q000378:metabolism*; D007276:Injections, Intraventricular; D007793:Lagomorpha; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D001127:Arginine Vasopressin; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D003345:Corticosterone; D009638:Norepinephrine