Hypoxic presser response, cardiac size, and natriuretic peptides are modified by long-term intermittent hypoxia

We investigated whether the effect of long-term intermittent hypoxia (LTIH) on cardiovascular function may be modified by preexisting genetic traits. To induce LTIH experimentally, cycles of 90-s hypoxia (nadir 6%) followed b y 90-s normoxia were applied to six Wistar-Kyoto and six spontaneously hype rtensive rats during 8 h daily. Comparison with the same number of control animals after 70 days revealed no alteration of intra-arterial blood pressu re or heart rate. Blood pressure responsiveness to a brief hypoxic stimulus was enhanced in the LTIH animals, regardless of strain, whereas the hypoxi a-induced increase in heart rate was abolished. In the spontaneously hypert ensive but not the Wistar-Kyoto rats, LTIH increased left ventricular weigh t-to-body weight ratio and content of atrial natriuretic peptide mRNA. Expr ession of B-type natriuretic peptide was unchanged (Northern blot). Slightl y increased right ventricular weight-to-body weight ratios in the LTIH anim als were associated with higher right ventricular atrial natriuretic peptid e and B-type natriuretic peptide mRNA amounts. Consequently, the effects of LTIH on different components of cardiovascular function appear incompletel y related to each other and differentially influenced by constitutional tra its.