RIGHT-VENTRICULAR COLLAGEN TYPE-III AND TYPE-IV GENE-EXPRESSION INCREASES DURING EARLY PHASES OF ENDURANCE TRAINING IN HYPOBARIC HYPOXIC CONDITION

The objective of this study was to examine the effects of prolonged ex posure to hypobaric hypoxic condition, physical training and their com bination on collagen type I, III and IV gene expression in the ventric les and atria of rat heart. Male rats were assigned to four groups: no rmobaric sedentary ( NS) and trained (NT), and hypobaric sedentary (HS ) and trained (HT). Exposure to and treadmill running training in hypo baric condition were carried out in a hypobaric chamber (770-740 mbar, 2250-2550 m). Experimental periods were 10, 21 and 56 days; the group s of 91 days served as recovery groups from experimental settings of 5 6 days. Exposure to hypobaric condition as such and in combination wit h endurance training for 10 days increased right ventricular weigth-to -body weight ratio (RV/BW) by 2.6 % (p < 0.001) and 23 % (p < 0.01), r espectively, when compared to 10NS. RV/BW was significantly increased also in 21HT and 56HT. Left ventricular weight-to-body weight ratio wa s 13 % (p < 0.01) and 14 % (p < 0.01) higher in 21HT and 56HT, respect ively, than in the respective NS. Right ventricular collagen type III mRNA level was 33 % (p = 0.065) and 38 % (p < 0.01) higher in 10HT tha n in 10NS and 10NT, respectively. Right ventricular collagen type IV m RNA level was 29 % (p < 0.001) higher in 10HT than in 10NS. Relatively slight left ventricular hypertrophy was not associated with significa nt changes in collagen mRNA levels. Decreased left ventricular subepic ardial prolyl 4-hydroxylase activity in 10HS and 10HT suggests transie nt corresponding decrease in the rate of collagen synthesis. This stud y shows that combination of endurance training and moderate hypobaric hypoxic condition leads to increased right ventricular collagen type I II and IV gene expression associated with right ventricular hypertroph y.