19 out of 20
All are actions of Endothelin 1 except (AIIMS May 2007)
Ans. A Bronchodilatation
- There are three isoforms of endothelin - Endothelin1 ,2,3. Endothelin 1 is found in plasma
- Endothelin 2 is found in kidney, G.I.T. (functional significance unknown)
- Endothelin 3 is found in CNS
- These endothelin act through two types of receptors:
- Endothelin A
- Endothelin B
- Both are G protein coupled (Gq type) which act by increasing intracellular calcium ions.
- But functionally they exert contrast properties:
- Endothelin A causes vasoconstriction ~ decreased GFR Endothelin B causes vasodilatation by increasing NO release.
- Clinical importance: Thus, when we use endothelin antagonist for pulmonary hypertension, it is better to use endothelin A selective antagonist (sitaxentan) instead of a nonselective antagonist (Bosentan)
- Both are pro-mitogenic.
- No specific action on bronchial smooth muscle.