Differential regulation of G protein expression in rat hearts exposed to chronic hypoxia.
Chronic hypoxia impairs adrenergic responsiveness. A modulation of Gs and/or G1 protein alpha-subunits may be associated with the downregulation of the beta-adrenergic receptors previously found in chronic hypoxia. G protein gene expression and protein level and function in rat hearts exposed to a 30-day hypobaric chronic hypoxia were compared with control rat hearts. No change was observed in G alpha s mRNA levels in either right or left ventricles. In right ventricles, mRNA levels of G alpha i-2 increased by 40% (P < 0.05), but not in left ventricles. In both left and right ventricles, chronic hypoxia did not modify G alpha i-2 and G alpha s protein amounts, but significantly decreased functional activity of G alpha s. In conclusion, gene expression, protein levels of G alpha s and G alpha i-2, and activity of G alpha s do not change in parallel fashion with chronic hypoxia. In chronic hypoxic right ventricles, although the mRNA level of G alpha i-2 is increased, the protein level is unchanged. One potential mechanism of desensitization to catecholamines in chronic hypoxia appears to involve a decreased functional activity of G alpha s in spite of normal mRNA and protein levels.
Kacimi
R
R
Institut National de la Santé et de la Recherche Médicale (INSERM) Unité U400, Créteil, France.
Moalic
J M
JM
Aldashev
A
A
Vatner
D E
DE
Richalet
J P
JP
Crozatier
B
B
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002908:Chronic Disease; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D012333:RNA, Messenger; D019204:GTP-Binding Proteins