[Cardiovascular benefits and hazard of physical practice]

Blood pressure response to isometric exercise in patients with peripheral atherosclerotic disease

BACKGROUND

The purpose of this study was to compare the circulatory responses to isometric exercise in patients with peripheral atherosclerotic disease (PAD) with healthy controls.

METHODS

Eleven patients with diagnosed PAD, a control group of eleven healthy young adults, and a control group of eleven healthy age-matched adults participated. Blood pressure, heart rate, stroke volume, cardiac output, blood velocity in the brachial artery, acral skin perfusion was continuously recorded and total peripheral resistance calculated before, during and after 2 min of 40% maximum voluntary contraction of the forearm.

RESULTS

At rest we found a consistently higher level of mean arterial pressure (MAP) and systolic pressure (SP) in the elderly, both PAD patients and elderly controls, compared with the young controls. We found no significant difference in diastolic blood pressure. Two minutes isometric handgrip exercise induced a similar increase in MAP in all three groups (patients 32.6 (17.9) mm Hg [mean (SD)], young control group 25.3 (8.9) mm Hg, age-matched control group 36.1 (10.6) mm Hg). No significant differences were found in the other measured cardiovascular variables during isometric handgrip. Increased TPR is the main factor contributing to the increase in blood pressure in all three groups.

CONCLUSION

Our study indicates that the pressor response continues to be well regulated with age, also when the cardiovascular system is altered by marked atherosclerosis. The consequence is that both PAD patients and elderly controls reach higher SP values during isometric exercise due to higher SP baseline values.

Alterations of beta3-adrenoceptors expression and their myocardial functional effects in physiological model of chronic exercise-induced cardiac hypertrophy

Physical training induces cardiovascular autonomic nervous system regulation adaptations, which could result from beta adrenergic receptor (AR) modifications. Among them, beta(3 )AR alterations have been recently reported but their functional effect remained to discuss. To explain the beta(3) AR gene expression in relation to function, we simultaneously studied the left ventricle (LV) beta(3) AR mRNA and protein levels and the myocardial functional effects of a beta(3) AR agonist following physical training. Forty rats were assigned to either a control (C; N = 20) or a trained (T; N = 20) group. The treadmill running protocol was performed for 8 weeks. Histological measurements on LV slices were quantified. The beta(3) AR mRNA abundance was studied with RT-PCR and beta(3) AR protein density with Western-Blot analysis. Myocardial functional effects of a beta(3) AR agonist, BRL37344 (10(-8) M), were studied in Langendorff-perfused hearts. Histological data confirmed the adapted patterns of the physiological cardiac hypertrophy observed in T (P < 0.01), with a significant increase in arteries density (P < 0.01) and an unchanged collagen concentration. The beta(3) AR protein density was increased in T (154 +/- 38% in T vs. 100 +/- 24% in C; P < 0.05), but no change was noted concerning the beta(3) AR mRNA level. After BRL37344 perfusion LVDP, +dP/dT and -dP/dT, in C (P < 0.01), and only +dP/dT in T (P < 0.05) were decreased. Moreover, all LV hemodynamic parameters were more altered after BRL37344 in C than in T (P < 0.01).Thus, in this physiological model of cardiac hypertrophy, an increase of beta(3) AR density without beta(3) AR mRNA alteration was observed. Classical negative myocardial lusitropic and inotropic effects induced by a specific agonist of beta(3) AR were diminished in trained rats.