title: Pretranslational regulation of two cardiac glucose transporters in rats exposed to hypobaric hypoxia.
abstract: To investigate the mechanism by which cardiac glucose utilization increases during hypoxia and increased work load, we studied the effect of 2 and 14 days of hypobaric hypoxia on the expression of two subtypes of the facilitative D-glucose transporter, the GLUT-4 or "insulin-regulatable" isoform and the GLUT-1 isoform thought to mediate basal transport. Rats lose weight when exposed to hypobaric hypoxia, so fasting controls were used in the 2-day studies and pair-fed controls in the 14-day experiments. Hypobaric hypoxia (PO2 69 mmHg) resulted in right ventricular (RV), but not left ventricular (LV), hypertrophy. RV and LV GLUT-1 mRNA levels increased 2- to 3-fold after 2 days and 1.5- to 2-fold after 14 days of hypobaric hypoxia compared with both fasted rats and normal controls. RV GLUT-1 protein increased approximately 3-fold and LV GLUT-1 protein increased 1.5-fold after 14 days of hypobaric hypoxia vs. both pair-fed and normal controls. RV GLUT-4 mRNA decreased to 26% and RV GLUT-4 protein decreased to 54% of normal control levels as a result of 2 days of hypobaric hypoxia. RV GLUT-4 mRNA decreased to 64% of normal control levels with no change in RV GLUT-4 protein as a result of 2 days of fasting. We conclude that hypobaric hypoxia increases cardiac GLUT-1 expression at the pretranslational level in both ventricles. The greater increase in GLUT-1 protein on the right suggests an additive effect of pressure overload. GLUT-4 expression is reduced early in the development of RV hypertrophy.
authors.affiliation: Department of Internal Medicine, Iowa City Veterans Affairs Hospital, Iowa.
authors.forename: W I
authors.initials: WI
authors.lastname: Sivitz
authors.forename: D D
authors.initials: DD
authors.lastname: Lund
authors.forename: B
authors.initials: B
authors.lastname: Yorek
authors.forename: M
authors.initials: M
authors.lastname: Grover-McKay
authors.forename: P G
authors.initials: PG
authors.lastname: Schmid
mesh_terms: D000818:Animals; D001274:Atmospheric Pressure; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D006352:Heart Ventricles; D000860:Hypoxia / Q000209:etiology / Q000378:metabolism*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins; D009206:Myocardium / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; C495694:Slc2a4 protein, rat