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Microsomal preparations of normal bovine iris-ciliary body generate prostacyclin-like but not thromboxane-A2-like activity

Authors :
Helena M. T. Eakins
Willian L. Saber
Kenneth E. Eakins
Prasad S. Kulkarni
Source :
Prostaglandins. 14:689-700
Publication Year :
1977
Publisher :
Elsevier BV, 1977.

Abstract

Indomethacin-treated bovine iris-ciliary body microsomes (IBIM) have been studied for their ability to convert PG endoperoxides into either thromboxane-A2 (TxA2)-like or prostacyclin (PGI2)-like activity. The biological activity of the ocular tissue microsomes were compared with either indomethacin-treated human platelet microsomes (for TxA2-like activity) or rabbit aorta microsomes (for PGI2-like activity) under appropriate incubation conditions. No evidence could be found for the formation of TxA2-like activity from PG endoperoxides by the IBIM. In contrast, when the IBIM were incubated with PGH2 for 1 min at 22 degrees C without cofactors, PGI2-like activity was produced, causing profound relaxation of the isolated dog coronary artery preparation without contracting the rabbit aorta and inhibiting arachidonic acid-induced platelet aggregation. Equivalent quantities of boiled IBIM failed to alter the biological activity of PGH2 under identical conditions. Tranylcypromine (500 microgram/ml) completely abolished the appearance of PGI2-like activity. Furthermore, the PGI2-like activity found was stable for 10 min at 22 degrees C at pH 8.5 but completely lost under similar conditions at pH 5.5. It is concluded that microsomal preparations of normal bovine iris-ciliary body can synthesize PGI2-like activity in substantial amounts but not TxA2-like activity.

Details

ISSN :
00906980
Volume :
14
Database :
OpenAIRE
Journal :
Prostaglandins
Accession number :
edsair.doi.dedup.....c2882fe38be415bd3eb3b03132fd8ba7
Full Text :
https://doi.org/10.1016/0090-6980(77)90196-4