Intraocular pressure and vascular effects of sodium azide in bovine perfused eye.
The effects of the nitrovasodilator, sodium azide, on intraocular pressure (IOP) and ciliary vascular tone were compared. IOP was measured in the bovine isolated eye that was perfused via the ciliary artery. Separately, vasodilator effects were assessed after raising the vascular tone using noradrenaline (10 microM). Aqueous humor formation (AHF) rate was estimated by a fluorescein dilution method. Cyclic GMP in the ciliary processes was measured by radioimmunoassay. When compared with controls, sodium azide (10 nmole bolus dose) was found to lower IOP (2.2 +/- 0.3 mm Hg; P < 0.01) via a reduction in AHF (12.19 +/- 0.26 microl/min to 6.36 +/- 0.53 microl/min; P < 0.001). Azide (1 micromole) also reduced ciliary vascular resistance (81.0 +/- 5.5%; P < 0.01). However, the drug was 20x more potent as an ocular hypotensive than as a vasodilator (ED50 0.28 nmole on IOP, 5.55 nmole on vascular effect). Azide (10 nmole) also increased levels of ciliary cyclic GMP (127 +/- 17 fmol/mg protein to 233 +/- 27 fmol/mg protein; P < 0.01). The IOP-lowering effect of azide does not appear to depend on its ability to activate guanylyl cyclase (GC) in vascular smooth muscle, but rather is likely a consequence of direct activation of ciliary epithelial GC.
Millar
J C
JC
Department of Biology and Health Science, University of Luton, Bedfordshire, England.
Shahidullah
M
M
Wilson
W S
WS
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D002417:Cattle; D019842:Ciliary Arteries / Q000502:physiology*; D006152:Cyclic GMP / Q000378:metabolism; D015590:Fluorophotometry; D006162:Guanylate Cyclase / Q000378:metabolism; D007429:Intraocular Pressure / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010477:Perfusion; D011863:Radioimmunoassay; D019810:Sodium Azide / Q000494:pharmacology*; D014655:Vascular Resistance / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D020030:Nitric Oxide Donors; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D019810:Sodium Azide; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D009638:Norepinephrine