Cardiac performance in elderly hypertensive patients with left ventricular hypertrophy: responses to isometric exercise and beta-agonists

β-adrenoceptors as molecular targets in the treatment of hypertension

Regulation of sympathoadrenal activity has been a long-time target in the management of hypertension. Regulation of β-adrenoceptor (βAR) function has been the most therapeutically important of these targets. The development of effective antihypertensive treatments based on βAR antagonism paralleled the elucidation of the molecular basis of β-adrenergic effects by the family of βARs, which are members of the G-protein-coupled receptor (GPCR) superfamily. βARs serve as the extracellular face of the transmembrane signalling pathway that results in the consequent activation of heterotrimeric G-proteins and the activation of several other newly appreciated signalling molecules that include β-arrestins and GPCR kinases (GRKs). The aggregate effect of the activation of these signalling pathways mediates the response to βAR activation. Paradoxically, the hypertensive state is characterized by impaired βAR responsiveness. This defect is common to many other receptor systems linked to the stimulator G protein (Gs) and adenylyl cyclase activation. This impairment is principally mediated by receptor-G-protein uncoupling, which has been linked to increased expression and activity of GRK2.

Arterial pulsatile hemodynamic load induced by isometric exercise strongly predicts left ventricular mass in hypertension

Although resting hemodynamic load has been extensively investigated as a determinant of left ventricular (LV) hypertrophy, little is known about the relationship between provoked hemodynamic load and the risk of LV hypertrophy. We studied central pressure-flow relations among 40 hypertensive and 19 normotensive adults using carotid applanation tonometry and Doppler echocardiography at rest and during a 40% maximal voluntary forearm contraction (handgrip) maneuver. Carotid-femoral pulse wave velocity (CF-PWV) was measured at rest. Hypertensive subjects demonstrated various abnormalities in resting and induced pulsatile load. Isometric exercise significantly increased systemic vascular resistance, aortic characteristic impedance (Zc), induced earlier wave reflections, increased augmentation index, and decreased total arterial compliance (TAC; all P < or = 0.01). In hypertensive subjects, CF-PWV was the strongest resting predictor of LV mass index (LVMI) and remained an independent predictor after adjustment for age, gender, systemic vascular resistance, reflection magnitude, aortic Zc, and TAC (beta = 2.52 m/s; P < 0.0001). Age, sex, CF-PWV, and resting hemodynamic indexes explained 48% of the interindividual variability in LVMI. In stepwise regression, TAC (beta = -17.85; P < 0.0001) during handgrip, Zc during handgrip (beta = -150; P < 0.0001), and the change in the timing of wave reflections during handgrip (beta = -0.63; P = 0.03) were independent predictors of LVMI. A model that included indexes of provoked hemodynamic load explained 68% of the interindividual variability in LVMI. Hemodynamic load provoked by isometric exercise strongly predicts LVMI in hypertension. The magnitude of this association is far greater than for resting hemodynamic load, suggesting that provoked testing captures important arterial properties that are not apparent at rest and is advantageous to assess dynamic arterial load in hypertension.

Effects of the long-acting calcium channel blocker barnidipine hydrochloride on 24-h ambulatory blood pressure

The effect of the long acting calcium channel blocker, barnidipine hydrochloride (barnidipine) on 24-h ambulatory blood pressure (ABP) was evaluated in J-MUBA (Japanese Multicentre Study on Barnidipine with Ambulatory Blood Pressure Monitoring). Following an observation period of two weeks, antihypertensive treatment with barnidipine was continued for at least six months. At the end of each period, ABP were measured. The patients were divided into high- and low-range groups based on ABP measurement. Throughout the 24 h, barnidipine exerted an excellent antihypertensive effect in the high-range group, but not in the low-range group. Barnidipine had comparable effects in the daytime and nighttime in inverted dippers and non-dippers, but it was more effective on daytime ABP than on nighttime ABP in dippers and in extreme dippers. Morning blood pressure before and after waking was evaluated before and after barnidipine administration in 233 patients. Barnidipine inhibited increases in blood pressure before and after waking, especially in surge-type patients whose blood pressure increased rapidly after waking. A positive correlation among 24-h ABP, daytime and night time ABP, morning blood pressure, and clinic blood pressure during the observation period and the antihypertensive effect of barnidipine was observed, with barnidipine exhibiting stronger antihypertensive effects in patients with persistently high blood pressure. It was concluded that the antihypertensive effects of barnidipine are maintained for 24 h but it has no excessive hypotensive effects on lower blood pressure and is thus a safe antihypertensive agent.