INDUCTION OF CARDIAC NATRIURETIC PEPTIDE GENE-EXPRESSION IN RATS TRAINED IN HYPOBARIC HYPOXIC CONDITIONS

Induction of cardiac natriuretic peptide gene expression in rats train ed in hypobaric hypoxic conditions, Am. J. Physiol. 273 (Regulatory In tegrative Comp. Physiol. 42): R344-R352, 1997.-Adaptation of cardiac m uscle to prolonged hypobaric hypoxia (770-740 mbar, 2,250-2,550 m), en durance training, and their combination was studied in rats by investi gating the gene expression of atrial natriuretic peptide (ANP) and B-t ype natriuretic peptide (BNP) in atria and ventricles. Rats were assig ned into the following groups according to the barometric conditions a nd physical activity: normobaric sedentary (NS), normobaric training, hypobaric sedentary (HS), and hypobaric training (HT). Experimental pe riods were 10, 21, and 56 days; the groups at 91 days served as recove ry groups from exposure to and training in normobaric and hypobaric co nditions for 56 days. The right ventricular hypertrophy in HT rats at 10 days and 56 days was associated with elevated BNP mRNA levels (2.1- and 1.7-fold, P < 0.05, respectively), whereas hypobaric exposure wit hout training was not sufficient to significantly increase ventricular BNP gene expression, although it lead to hypertrophy of the right ven tricle. Right and left atrial BNP mRNA levels were also increased (up to 3.9-fold, P < 0.01) in 10-day HS and 10-day HT groups. ANP mRNA lev els in right ventricle and left. ventricular epicardium were over twof old higher (P 0.05-0.01) in 10-day HS and 10-day HT groups in comparis on to 10-day NS group. Plasma immunoreactive ANP concentration was inc reased (P < 0.05) in both hypobaric groups up to 21 days. The results show that exposure to hypobaric hypoxia itself and endurance training in hypobaric, hypoxic conditions lead to a marked early increase in ve ntricular and atrial ANP and BNP mRNA levels. The adaptational respons e to hypoxia was more pronounced when the oxygen availability was lowe red additionally by endurance training carried out in hypobaric hypoxi c conditions.