Effects of Antiglaucoma Drugs on [32P]Orthophosphate Incorporation into Phospholipids of Cat Iris and Ciliary Process

Thomas Yorio, George Deloach, Nimman Satumtira

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

The effects of antiglaucoma drugs on [32P]-orthophosphate incorporation into phospholipids of iris and ciliary process were investigated. Both iris and ciliary process rapidly incorporated 32Pi into the major phospholipids, with the acidic phosphoinositides demonstrating a greater labelling than phosphatidylcholine, indicating a greater turnover. The muscarinic agonists, carbachol and pilocarpine, stimulated 32Pi-labelling of phosphatidylinositol (PI) and phosphatidic acid (PA) in both iris and ciliary process. These effects were blocked by atropine, suggesting that the response was mediated through muscarinic receptors. The beta blocking ocular hypotensive drugs, propranolol, timolol and atenolol, produced varying effects on 32P incorporation into phospholipids of iris and ciliary process. Propranolol stimulated 32Pi-labelling into phosphatidylinositol 4′, 5′ bisphosphate (PIP2), phosphatidylinositol 4′ phosphate (PIP), PI and PA. Timolol decreased 32Pi-incorporation into PIP2 and PI, whereas atenolol, a selective beta1 antagonist, had no significant effect on 32Pi-labelling of phospholipids. The above findings on propranolol agree with previous observations which demonstrated that propranolol redirects glycerolipid metabolism through multiple effects on the enzymes in phospholipid biosynthesis, particularly in stimulating phosphatidylinositol kinases. The results with timolol suggest that this drug may decrease phosphoinositide hydrolysis. The effects of these ocular hypotensive, non-selective beta blocking drugs on phospholipid turnover may ultimately limit the accumulation of breakdown products which could serve as cellular messengers.

Original languageEnglish
Pages (from-to)245-254
Number of pages10
JournalJournal of Ocular Pharmacology
Volume1
Issue number3
DOIs
Publication statusPublished - 1 Jan 1985

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