NT-proBNP Canine

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a crucial biomarker in veterinary medicine, particularly for diagnosing and managing cardiac diseases in dogs. This peptide is a fragment of the prohormone BNP (B-type natriuretic peptide), which is produced by cardiac muscle cells (cardiomyocytes) in response to excessive stretching of the heart muscle.

BNP is synthesized as a precursor prohormone, which is then cleaved into two fragments: the bioactive C-terminal BNP (C-BNP) and the inactive N-terminal proBNP (NT-proBNP). While C-BNP has a short half-life of approximately 90 seconds, NT-proBNP has a longer half-life of about 120 minutes, making it more stable and easier to measure in clinical settings .

BNP is primarily produced in the ventricles of the heart. The expression of BNP increases significantly in response to conditions that cause cardiac stress, such as heart failure, myocardial infarction, and other forms of cardiac disease. The increased production of BNP and its subsequent cleavage into NT-proBNP serves as a compensatory mechanism to reduce cardiac workload by promoting vasodilation and natriuresis (excretion of sodium in the urine) .

The primary function of BNP, and by extension NT-proBNP, is to regulate blood pressure and fluid balance. BNP promotes the excretion of sodium and water by the kidneys, leading to a reduction in blood volume and pressure. This helps to alleviate the stress on the heart by decreasing the volume of blood it needs to pump .

BNP acts by binding to specific receptors on the surface of target cells, leading to the activation of intracellular signaling pathways that result in vasodilation and natriuresis. The actions of BNP counteract the effects of the renin-angiotensin-aldosterone system (RAAS), which is often upregulated in heart disease and contributes to increased blood pressure and fluid retention .

NT-proBNP is a valuable biomarker for diagnosing and monitoring heart disease in dogs. Elevated levels of NT-proBNP in the blood are indicative of cardiac stress and can help differentiate between cardiac and non-cardiac causes of clinical signs such as coughing, dyspnea, and exercise intolerance . This biomarker is particularly useful in identifying preclinical stages of cardiac disease, allowing for early intervention and management .

The production and release of BNP are regulated by various factors, including mechanical stress on the heart, neurohormonal activation, and inflammatory cytokines. The cleavage of proBNP into NT-proBNP and C-BNP is mediated by the enzyme corin, which is expressed on the surface of cardiomyocytes .