Only when the hormone endothelin is present in the bloodstream will the arteriole smooth muscle of the pulmonary system and bronchioles contract and undergo vasoconstriction. In many cases, this can be a problem as pulmonary hypertension (elevated blood pressure) can cause certain health problems and if persistent is a risk factor for stroke, myocardial infarction and heart failure.
The reason why this can be a problem exists in the way in which endothelin provokes vasoconstriction of the pulmonary arterioles - it isn't clear at present. Endothelin is a natural occurring metabolite which is produced in the endothelium and serves; it seems, to promote the constriction of arterioles to prevent heat loss or to reverse vasodilation and so conserve a healthy state of homeostasis. They are the strongest vasoconstrictors known which explains why they are so commonly used and why there are plenty of endothelin receptors in the body, specifically in blood vessels, brain cells and peripheral nerves. However, imbalances and dysregulation of endothelin in the lungs can occur and result in pulmonary hypertension, which is categorized by shortness of breath (most noticeable when lying down - orthopnea), dizziness and angina pectoris. However, given that most of these symptoms seem harmless, most people will put off seeking medical advice which is unwise as pulmonary hypertension can be a severe disease which can result in heart failure. When imbalances occur randomly around the body, it can cause:
• Cancers
• Cerebral vasospasm (spasms of blood vessels) which can lead to subarachnoid haemorrhage.
• Arterial hypertension and other cardiovascular disorders.
High concentrations of endothelin can be regulated by endothelin receptor antagonists such as ambrisentan, bosentan and sitaxentan. Doses of such medicine must be carefully adhered to as over-exposure to these drugs can have adverse effects too such as liver enzyme abnormalities, upper respiratory tract infection and insomnia.
The reason why this can be a problem exists in the way in which endothelin provokes vasoconstriction of the pulmonary arterioles - it isn't clear at present. Endothelin is a natural occurring metabolite which is produced in the endothelium and serves; it seems, to promote the constriction of arterioles to prevent heat loss or to reverse vasodilation and so conserve a healthy state of homeostasis. They are the strongest vasoconstrictors known which explains why they are so commonly used and why there are plenty of endothelin receptors in the body, specifically in blood vessels, brain cells and peripheral nerves. However, imbalances and dysregulation of endothelin in the lungs can occur and result in pulmonary hypertension, which is categorized by shortness of breath (most noticeable when lying down - orthopnea), dizziness and angina pectoris. However, given that most of these symptoms seem harmless, most people will put off seeking medical advice which is unwise as pulmonary hypertension can be a severe disease which can result in heart failure. When imbalances occur randomly around the body, it can cause:
• Cancers
• Cerebral vasospasm (spasms of blood vessels) which can lead to subarachnoid haemorrhage.
• Arterial hypertension and other cardiovascular disorders.
High concentrations of endothelin can be regulated by endothelin receptor antagonists such as ambrisentan, bosentan and sitaxentan. Doses of such medicine must be carefully adhered to as over-exposure to these drugs can have adverse effects too such as liver enzyme abnormalities, upper respiratory tract infection and insomnia.
