Question

Travis, an overweight 51 year old male, had been diagnosed with stable angina two years ago and was prescribed sublingual nitroglycerin to be taken as needed. Recently, his attacks have become more frequent and less predictable. During his annual check up, his doctor looked alarmed when his blood test revelled elevated cardiac troponin levels.

A) Describe the function of troponin in healthy cardiomyocytes?

B) Explain why Travis' doctor was alarmed at his blood test results. Why did his serum cardiac troponin levels increase?

Answer 1

A) Troponins are proteins, mainly found in the cardiac and skeletal muscle fibres which helps in muscle contraction. There are three subunits of troponins seen in cardiomyofibrils. Cardiac troponin (cTn), cardiac troponin I (cTnI) and cardiac troponin T (cTnT). Its function is the contraction of cardiac muscles. It is by the function of calcium induced calcium production where Ca 2+ induces the troponin and thus troponin sits on tropomyosin which causes myosin to attach with actin which causes contraction.
What is the function of Troponins?
They are important for muscle contraction in the heart. It is regulated by the Ca2+ level. It is called Calcium Induced Calcium Release(CICR). When it increases, it binds to troponin C, forms a comples with all the subunits, then troponin displaces tropomyosin and thus myosin can easily bind to actin and contraction happens.

B) According to Travi's medical histroy, he has been suffering with angina, which is a continous pain, squeezing feel or pressure in heart may be due to any coronary heart disease. He has been taking Nitroglycerin sublingual tablets which is taken for chest pain. His troponin levels are elevated in his blood results. It is an evidence of heart disease mainly heart attack. It can also occur due to kidney failure, other diseases etc.. But foe Travis, it is more likely due to cardiac issues. Heart attacks are mainly occuring due to less supply of oxygen and nutrients to heart cells. It is due to the blockage or narrowing of the coronary arteries. When cardiac muscles lack oxygen, the cell disrupts due to cardiac attack. It causes the troponin in heart muscle cells drain into the blood. Thus the presence of troponin in blood and its concentration clearly suggests that the patient has suffered a cardiac attack. If the level is too high, then the person is more likely to get serious cardiac problems which may be lethal. That's why Travi's doctor was alarmed. Troponin may appear within 6 hours and last for almost 14 days. If the troponin levels are high, emergency medical treatment should be taken.
As the cell ruptures and troponin get into the bloodstream, the contraction process gets disrupted.