Cardiac β-adrenergic responsiveness with exercise

Abstract

Left ventricular performance is enhanced with chronic exercise training. Alterations in cardiomyocyte β-adrenergic responsiveness (BAR) may, in part, mediate this response. In this study, cardiac BAR and the expression of some key cardiac hypertrophic signaling molecules following 3 months of treadmill training were examined. Four-month old, female, Wistar Kyoto (WKY) rats were randomly assigned into either a sedentary (WKY-SED, n = 15) or an exercise-trained (WKY-TRD, n = 11) group. All rats were maintained on a 12-h light/dark cycle, and fed ad libitum. Exercise training consisted of motorized treadmill training at 25 m/min, 0% grade, 60 continuous minutes, 5 days/week for a period of 12 weeks. RT-PCR was used to establish basal cardiac calcineurin A, ANP, and AKT mRNA expression. In vitro cardiac BAR responsiveness was determined in Langendorff, isolated hearts. Following baseline, isoproterenol (ISO) was incrementally infused at concentrations ranging from 1 × 10(-10) to 1 × 10(-7) mol/L. There were no group differences for heart weight, heart to body weight ratio, calcineurin A, ANP, or AKT mRNA levels between WKY-SED and WKY-TRD. WKY-TRD showed enhanced cardiac BAR relative to WKY-SED (at ISO 1 × 10(-7) mol/L; P < 0.05). Moderate intensity treadmill exercise improved cardiac BAR responsiveness to a high concentration of isoproterenol. This adaptation was independent of training-induced alterations in cardiac hypertrophy or hypertrophic marker expression.

Neuronal nitric oxide synthase is indispensable for the cardiac adaptive effects of exercise

“…Remarkably, acute NOS1 inhibition (+SMLT) normalized Ex myocyte contraction (Ca 2+ transients and cell shortening amplitude) and Ca 2+ decline to Sed myocyte levels (Fig 1D-F). In addition, Ex myocytes had a greater functional response (Ca 2+ transient and shortening amplitudes) to β-adrenergic receptor (β-AR) stimulation with isoproterenol (ISO) (Fig 1H), consistent with previous studies in animals and humans [34, 41, 53, 55]. As with basal contraction, acute NOS1 inhibition (+SMLT) abolished the increased functional response to low dose ISO in Ex myocytes.…”

The mitochondrial signaling peptide MOTS-c improves myocardial performance during exercise training in rats

“…Therefore, we tested the myocardial ANP and BNP mRNA and found that the ANP mRNA in the ME group was significantly increased, and that ANP mRNA levels in rats from group E tended to increase, but with was no changes in BNP mRNA levels. The Libonati team conducted a 12-week treadmill exercise intervention on Wistar rats and reported no changes in ANP mRNA in the exercise and the sedentary groups 42 , which is consistent with the results of our study. In addition, BNP levels did not change significantly in exercised rats 43 , similar to the results of our study as well.…”

Physical activity ameliorates cardiovascular health in elderly subjects: the functional role of the β adrenergic system

“…An increased responsiveness to isoproterenol has been demonstrated in the myocardium of trained rodents, when compared with sedentary controls (Takeda et al, 1985; Libonati and MacDonnell, 2011). Such responses have been shown to be independent of training-induced alterations in cardiac hypertrophy or hypertrophic marker expression.…”