AUTOREGULATION-PGI2 vs TXA2

SUMMARY

PGI-2
1. Prostacylin (PGI-2) produced by endothelial & smooth muscle cells in blood vessels
2. PGI-2 inhibits platelet aggregation & promote vasodilation.

TXA-2
3. Thromboxane A2 (TXA-2) released from platelets, derived from arachnidonic acid via COX pathway.
4. TXA-2 promotes platelet aggregation & vasoconstriction, thus promoting ‘plug’ formation.

BALANCE!
5. Balance between the 2 controls localized clot formation, while maintaining distal blood flow.
6. Aspirin shift this balance towards PGI-2 by irreversible inhibition of cyclooxygenase.

Reference(s)

Barrett, K.E., Barman, S.M., Boitano, S., Brooks, H.L., Weitz, M., Brian Patrick Kearns, Ganong, W.F. and Mcgraw-Hill Education (Firm (2016). Ganong’s review of medical physiology. 25th ed. New York: Mcgraw Hill Education.
Hall, J.E. and Hall, M.E. (2020). Guyton And Hall Textbook Of Medical Physiology. 14th ed. S.L.: Elsevier - Health Science.
West, J.B. and Luks, A.M. (2021). West’s Pulmonary Pathophysiology. Lippincott Williams & Wilkins.