Effects Of Hypoxia On HPA Axis Activities Of Three Plateau Animals

Every stressor and stimuli will influence organ's functions.Thus being considered as one of the special environmental stressor,high altitude hypoxia can disturb metabolism which will result in some abnormal reactions including anorexia, headache,nausea,dizziness,etc.Ochotona Curzoniae,Microtus Oeconomus,and Myospalax Baileyi,which are native mammals of Qinghai-Tibetan plateau and have well acclimated to hypoxia.This study reports the effects of hypoxia on CRF secretion from ME of hypothalamus,which plays a central role in the regulation of HPA axis.This study also reports different effects of hypoxia on the secretions of corticosterone and cortisol in plasma.Hypoxia was simulated by two methods:the cobalt chloride(CoCl₂)treatment and the normobaric chamber,CRF and cAMP were determined by RIA,Corticosterone and cortisol by EIA.Research design and Methods1.To investigate the activities of HPA axis under hypoxia,Ochotona curzoniae and Myospalax Baileyi were exposed to CoCl₂-induced hypoxia.CRF,cAMP, Corticosterone and Cortisol were tested by RIA and EIA respectively.2.To investigate the activities of HPA axis under hypoxia,Microtus oeconomus and Mus musculus were maintained in a box with a mixture of N₂/O₂(16.0%,10.8%and 8.0%O₂).Methods were the same as above.3.One pair of CRF primers were designed to clone CRF gene of Microtus oeconomusResults1.The changes of CRF in ME of Ochotona Curzoniae,Microtus Oeconomus, Myospalax Baileyi,and mice.During normobaric hypoxia condition,16.0%,10.8%O₂ or 8.0%O₂ hypoxia remarkably stimulated the release of CRF from ME of mice.The concentration of CRF in ME of Microtus Oeconomus did not change in 10.8%O₂ condition,whereas,it prominently decreased in 8.0%O₂ hypoxia;During CoCl₂ treatment,20mg/kg CoCl₂ treatment did not influence CRF in ME of Myospalax Baileyi,but 40mg/kg CoCl₂ treatment greatly stimulated the release of CRF in ME.And 40mg/kg CoCl₂ treatment did not influence CRF in ME of Ochotona Curzoniae.2.The changes of cAMP in pituitary of Ochotona Curzoniae,Microtus Oeconomus, Myospalax Baileyi,and mice.During normobaric hypoxia,16.0%,10.8%O₂ or 8.0%O₂ hypoxia remarkably increased concentration of cAMP in pituitary of mice.The concentration of cAMP in pituitary of Microtus Oeconomus did not change in 10.8%O₂,whereas,it prominently increased in 8.0%O₂ hypoxia;During CoCl₂ treatment,20mg/kg CoCl₂ treatment did not influence cAMP in pituitary of Myospalax Baileyi,but 40mg/kg CoCl₂ treatment greatly enhanced the concentration of cAMP in pituitary.And 40mg/kg CoCl₂ treatment also increased the concentration of cAMP in pituitary of Ochotona Curzoniae.3.The changes of plasma corticosterone of Ochotona Curzoniae,Microtus Oeconomus,Myospalax Baileyi,and mice.Plasma corticosterone of Ochotona curzoniae(40mg/kg)did not change;Myospalax Baileyi(20mg/kg)did not respond to CoCl₂ treatment,but 40mg/kg pronouncedly increased plasma corticosterone.Plasma corticosterone of Microtus oeconomus did not change during normobaric hypoxia(10.8%O₂),but remarkedly increased during 8.0%O₂ condition;16.0%,10.8%O₂ or 8.0%O₂ hypoxia remarkably enhanced plasma corticosterone secretion of mice.4.The changes of plasma cortisol of Ochotona Curzoniae,Microtus Oeconomus, Myospalax Baileyi,and mice.Plasma cortisol of mice and Microtus Oeconomus did not change in all the treatments. Plasma cortisol of Myospalax Baileyi did not change by 20mg/kg CoCl₂ treatment, whereas it remarkedly increased by 40mg/kg CoCl₂ treatment.The cortisol in plasma of Microtus Oeconomus pronouncedly increased by 40mg/kg CoCl₂ treatment.4.The CDS of CRF of Microtus Oeconomus has 564 nucleotides,encoding 187 amino acids,and 91%,91%,79%and 77%identify with that of rat,mouse,human and pig respectively.Conclusions:1.Ochotona curzoniae,Microtus oeconomus and Myospalax Baileyi are well acclimatized to environmental hypoxia.Ochotona curzoniae might be de-sensitive or have high tolerance to hypoxia.Hypoxia had smaller effects on its CRF release from ME.2.Accoring to the CRF CDS sequence of Microtus oeconomus,it had high homonology to mice and rat.