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Cardiovascular hormones

Cardiovascular hormones. Dr J Ker. Previous lecture: Mechanical aspects, blood pressure, formulas… Now: Hormonal aspects of the cardiovascular system. Hormonal interactions:. Heart----brain Brain----heart Heart----kidney Kidney----heart. Heart---brain:. Group of natriuretic peptides.

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Cardiovascular hormones

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  1. Cardiovascular hormones Dr J Ker

  2. Previous lecture: Mechanical aspects, blood pressure, formulas… • Now: Hormonal aspects of the cardiovascular system

  3. Hormonal interactions: • Heart----brain • Brain----heart • Heart----kidney • Kidney----heart

  4. Heart---brain: • Group of natriuretic peptides. • ANP, BNP,C-type • Produced by atrial and ventricular myocardium • Produced in response to stretch, increased end-diastolic pressure • Physiological action: Acts as diuretic—natriuretic peptide • Decrease blood pressure

  5. Clinical application: • Diagnostic test for cardiac failure

  6. Opioid peptides • Produced by heart—ventricular myocardium. • Released during myocyte damage: MI • Acts as natural pain killers

  7. Angiotensin II. • Physiological action of angiotensin II: • Vasoconstriction: Increase blood pressure • Vasoconstriction of efferent arteriole in kidney: Increase intraglomerular pressure • Stimulate vascular growth—mitogen • Reabsorption of sodium in proximal tubule • Stimulate production of aldosterone • Increase sympathetic outflow • Stimulate thirst: hypothalamus

  8. Heart---kidney: • Natriuretic peptides • Angiotensin II

  9. Kidney---heart: • Renin-angiotensin-aldosterone system: • 2 pathways to angiotensin II production: • Via renin-angiotensin-aldosterone sustem • Via so-called non-ACE pathways.

  10. Renin-angiotensin-aldosterone system: • Renin: An enzyme produced by kidney: juxtaglomerular apparatus. • In response to: decrease in BP, increase in filtered sodium load. • Acts on: Angiotensinogen. A protein produced by liver. Converts to angiotensin I.

  11. Angiotensin converting enzyme(ACE): • Enzyme, produced by endothelium (especially pulmonary endothelium) • Converts Angiotensin I to angiotensin II • 3 Genotypes: • ACE-D/D • ACE-I/I • ACE-D/I

  12. Non-ACE pathways: • Various tissues: Heart, blood vessels, uterus, kidney: • Able to convert AT II to AT II without renin • Eg chymase • Also: Can produce AT II directly • Clinical implication: Drugs: ACE-inhibitors vs AT-II receptor blockers

  13. AT-II receptors: • > 7 known • 2 of clinical importance: • AT-II type I: Classic actions of angiotensin II • AT-II type II: Importance in CV-development, fetus • AT-II blockers: Blocks only AT-II type I receptors

  14. Aldosterone: • Hormone produced by adrenal cortex • Steroid hormone • Production is stimulated by AT-II • Physiological action: • Reabsorption of sodium, excretion of potassium and hydrogen: • Kidney: Cortical collecting duct • Sweat, saliva, gastric juice

  15. Conn syndrome: • Tumor of adrenal cortex, producing excess aldosterone: • Hypertension • Hypokalaemia • Alkalosis

  16. Brain---heart: • Sympathetic nervous system: • Acts on adrenal medulla: Increase catecholamines, increase in stroke volume and heart rate • Acts on kidney: Increase production of renin • Other hormones: Growth hormone: Trophic effect on heart

  17. Endothelium: • An organ • 2`nd largest organ in body • Largest=fat • Why an organ: It produces hormones • Weight of endothelium +/- 1.5 kg • Endothelium: 4 groups of functions:

  18. Maintains balance between vasoconstriction and vasodilatation: • NO, bradykinin, ANP: Vasodilatation • AT-II, thromboxane A2: Vasoconstriction

  19. Maintains balance between thrombosis and fibrinolysis: • Tissue factor (factor III): Thrombosis • T-PA: Tissue type plasminogen activator: Fibrinolysis

  20. Maintains balance between inflammation and anti-inflammatory mechanisms. • Endothelium produces adhesion molecules: ICAM, PECAM, VECAM etc

  21. Maintains balance between growth and apoptosis: • Angiotensin II: A growth factor, mitogen, causes hypertrophy of arterial intima

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