Endothelial Function Flashcards
What are the functions of endothelium?
Capillary transport, regulation of plasma lipids, control of hemostasis, white blood cell adhesion, and modulaton of vascular smooth muscle reactivity
What vasoactive substances are secreted by the endothelium?
Prostacyclin (vasodilation), endothelin (vasoconstrictor), nitric oxide (vasodilation), endothelial derived hyperpolarizing factor (vasodilation)
What endothelial enzyme degrades norepinephrine and other catecholamines, serotonin?
Monoamine oxidase
What structures allow for ion transfer between individual endothelial cells?
Myoepithelial Gap Junction
How does prostaglandin I2 mediate vasodilation?
Increases cAMP, activating PKA, which phosphorylates MLCK and decreases activity
What converts angiotensin I to angiotensin II?
Angiotensin converting enzyme (ACE)
What is the effect of Angiotensin II?
Vasoconstriction
When the endothelium is intact what platelet products cause vasodilation?
Vasopressin, ATP, ADP
What is the physiologic response to a severed capillary?
Platelet aggregation and vasoconstriction
What vasoconstrictive compound is produced by platelets?
Thromboxane
On what cells does Thrombin act? What is its effects?
Endothelial cells; vasodilation
How does the parasympathetic nervous system mediate vasodilation?
Acetylcholine binds to a muscarinic receptor on the endothelial cell, increasing calcium concentration which activates endothelial nitric oxide synthase, which converts L-arginine to nitric oxide. NO diffuses out to blood to inhibit platelet aggregation and out of the cendothelial cell to VSM and activates guanylyl cyclase, increasing cGMP, activating Protein kinase G and decreasing Ca++ and vasodilating
What are the variants of nitric oxide synthase?
neuronal (nNOS), endothelial (eNOs), and inducible (iNOS)
Which nitric oxide synthase variants require calcium?
eNOS
When is iNOS produced?
Severe infection
What is the effect of COX on vascular radius?
Vasodilative
True or False: cAMP and cGMP both elicit vasodilation of vascular smooth muscle
True
How does endothelial-derived hyperpolarizing factor mediate vasodilation?
It hyperpolarizes the membrane potential, causing it to be more negative and keeping v-gated calcium channels closed
What are the effects of epinephrine on vascular smooth muscle?
Epinephrine binds to beta-2 receptors, activating adenylyl cyclase and increasing cAMP
How does the Sympathetic nervous system mediate vasoconstriction?
NE binds alpha-receptors on VSM, activating PLC, increasing IP3, increasing Ca++
How does endothelin mediate vasoconstriction?
Activates PLC, increasing IP3, increasing Ca
What seems to the basis of hypertension?
Insufficient response to ACh because of damaged endothelium
What vessels are usually used for bypass surgeries? Which maintains patency better?
Saphenous vein or internal mammary artery; Internal mammary artery
