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Biochemistry

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Enzymes

Question
19 out of 20
 

All are actions of Endothelin 1 except (AIIMS May 2007)



A Bronchodilatation
B Vasoconstriction
C Decreased GFR
D Vasodilatation

Ans. A Bronchodilatation
  1. There are three isoforms of endothelin - Endothelin1 ,2,3. Endothelin 1 is found in plasma
  2. Endothelin 2 is found in kidney, G.I.T. (functional significance unknown)
  3. Endothelin 3 is found in CNS
  4. These endothelin act through two types of receptors:
  5. Endothelin A
  6. Endothelin B
  7. Both are G protein coupled (Gq type) which act by increasing intracellular calcium ions.
  8. But functionally they exert contrast properties:
  9. Endothelin A causes vasoconstriction ~ decreased GFR Endothelin B causes vasodilatation by increasing NO re­lease.
  10. 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)
  11. Both are pro-mitogenic.
  12. No specific action on bronchial smooth muscle.

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