Pindolol is a beta adrenoceptor antagonist used to treat hypertension, edema, ventricular tachycardias, and atrial fibrillation. It can be found under the brand names Viskazide and Visken. Pindolol is a first generation non-selective beta blocker used in the treatment of hypertension. Early research into the use of pindolol found it had chronotropic effects, and so further investigation focused on the treatment of arrhythmia. Blocking beta-1 adrenergic receptors in the heart results in decreased heart rate and blood pressure. Beta-1 receptors are G-protein-coupled receptors (specifically Gs alpha subunit) whose action is exerted through the cyclic AMP (cAMP) and cAMP-dependent protein kinase action with resultant calcium ion concentration increases. Increased intracellular calcium increase inotropy in the heart through calcium-induced exchange facilitated by the sarcoplasmic reticulum. Myosin light chains phosphorylated by PKA lead to contractility in muscle cells. Normally, activation of the beta-1 receptor in the heart increases sinoatrial (SA) nodal, atrioventricular (AV) nodal, and ventricular muscular firing, which leads to increased heart rate and contractility. Stroke volume and cardiac output will also increase as a result. In the kidney, renin is released when smooth muscle cells in the juxtaglomerular apparatus are activated. Blood volume is eventually increased because of the downstream production of angiotensin II and aldosterone production triggered by renin. Ordinarily, this adrenergic response results in increased inotropy, chronotropy, and dromotropy. The blockade of this pathway with beta-1 blockers results in decreased contractility (inotropy), decreased heart rate (chronotropy), increased relaxation (lusitropy), and decreased cardiac conduction times (dromotropy).

Pindolol B1-Adrenergic Cardiac Muscle Relaxation Pathway References