Contractility is the fundamental functional property of the heart enabling it to generate the force necessary to pump blood throughout the circulatory system. Contractility involves a variety of proteins, metal ions, and signalling pathways that together coordinate the contraction and relaxation of cardiomyocytes. The sarcomere is the basic contractile unit of muscle cells, including cardiomyocytes. It is composed of overlapping thick (myosin) and thin (actin) filaments. Contraction occurs as these filaments slide past each other, causing the sarcomere to shorten in length. The interaction between myosin and actin is the core of muscle contraction. ATP binding to myosin allows it to form a cross-bridge with actin. When ATP is hydrolysed, myosin changes its conformation, pulling on the actin filament thereby generating force. This process, known as the cross-bridge cycle, is repeated many times during muscle contraction. Calcium ions play a critical role in initiating and regulating muscle contraction. In resting cardiomyocytes, intracellular calcium levels are low due to active calcium pumps in the sarcoplasmic reticulum (SR) that sequester calcium. During contraction, an action potential triggers the release of calcium from the SR into the cytoplasm, allowing it to bind to troponin, a protein that facilitates the interaction between myosin and actin.The process by which an electrical signal (action potential) leads to muscle contraction is known as excitation-contraction coupling. When an action potential travels along the cell membrane (sarcolemma), it reaches the transverse tubules (T-tubules), which are invaginations of the sarcolemma. This triggers the release of calcium from the SR, initiating muscle contraction. The influx of calcium ions from extracellular fluid through voltage-gated calcium channels and the release of calcium from the SR are key steps in excitation-contraction coupling. Calcium binds to troponin, causing a conformational change that enables the actin-myosin interaction. Signaling pathways involving second messengers, such as cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA), also influence contractility. β-adrenergic receptors on cardiomyocytes are activated by epinephrine and norepinephrine, leading to increased cAMP levels and PKA activation. PKA phosphorylates various substrate proteins, including those involved in calcium handling and myofilament sensitivity to calcium, thereby enhancing contractility. Phospholamban is a regulatory protein that modulates the activity of the SR calcium pump (SERCA). Phosphorylation of phospholamban by PKA relieves its inhibition of SERCA, promoting faster calcium reuptake into the SR and thereby enhancing relaxation. Troponin I and myosin can also be phosphorylated by PKA. Troponin I phosphorylation reduces the affinity of troponin for calcium, enhancing relaxation, whilst myosin phosphorylation increases myosin's ATPase activity, increasing the rate of cross-bridge cycling and contractility. We provide a wide product catalogue of research reagents for studying myocardial contractility, including Hsp27 antibodies, Caldesmon antibodies, Angiotensin Converting Enzyme 2 antibodies, Cardiac Troponin I ELISA Kits, and Hsp27 ELISA Kits. Explore our full myocardial contractility product range below and discover more, for less. Alternatively, you can explore our Contractile Proteins and Inotropics product ranges.