Phalloidin inhibits epinephrine's and cytochalasin B's facilitation of aqueous outflow.
OBJECTIVE
To determine whether phalloidin, a fungal peptide that inhibits actin filament depolymerization, could inhibit the ability of cytochalasin B and epinephrine to increase the facility of aqueous outflow in the eyes of living cynomolgus monkeys.


METHODS
Outflow facility was determined by two-level constant-pressure perfusion of the anterior chamber. After measurement of baseline facility in both eyes, one eye of each animal received intracameral phalloidin (1.3, 13, or 130 mumol/L); the opposite eye received vehicle. Both eyes then received either epinephrine (0.3 mmol/L) or cytochalasin B (0.2 mmol/L), and facility was again measured.


RESULTS
Cytochalasin B and epinephrine increased facility by 120% to 190% and 100% to 180%, respectively (uncorrected for 15% resistance washout caused by perfusion itself). Phalloidin itself (13 or 130 mumol/L) did not affect facility, but it inhibited up to 50% of the facility-increasing effect of cytochalasin B and epinephrine.


CONCLUSIONS
We conclude that (1) the aqueous humor outflow facilitating effects of cytochalasin B or epinephrine depend in some manner on depolymerization of actin filaments within trabecular meshwork cells, and (2) actin filaments may help regulate aqueous outflow.
Robinson
J C
JC
Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison.
Kaufman
P L
PL
D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects* / Q000502:physiology*; D003571:Cytochalasin B / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004837:Epinephrine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D005260:Female; D008252:Macaca fascicularis; D010590:Phalloidine / Q000494:pharmacology*
D010590:Phalloidine; D003571:Cytochalasin B; D004837:Epinephrine