The effect of colchicine on the rate of formation of aqueous humour and the gross outflow facility in the albino rabbit.
Colchicine, a naturally occurring plant alkaloid which prevents the polymerisation of cytoplasmic microtubules, lowers the intraocular pressure after topical administration or intravitreal injection. In this study we have examined the effect of topically administered colchicine on the rate of formation of aqueous humour and the gross outflow facility in the albino rabbit eye. The disappearance of [14C]inulin from the anterior chamber was measured to calculate the rate of aqueous humour formation and in a separate group of animals the gross outflow facility determined using a constant pressure perfusion technique. Topically administered colchicine (10, 20 and 40 micrograms/eye) inhibited the rate of aqueous humour formation dose-dependently. The mean rate of formation in control eyes was 3.68 +/- 0.09 microliters/min (n = 16) decreasing to 1.8 microliter/min (n = 9) in eyes treated with 40 micrograms colchicine. Furthermore, the gross outflow facility of colchicine treated (10 micrograms/eye) eyes (0.49 +/- 0.03 microliter/min/mmHg) was significantly greater (P less than 0.05) than that of contralateral control eyes (0.39 +/- 0.03 microliter/min/mmHg). The pharmacological evidence available indicates that colchicine is acting via mechanisms of microtubule disruption to produce an ocular hypotensive response, suggesting that microtubules may be involved in the formation of aqueous humour and possibly the maintainance of cell shape and form in the outflow vessels of the anterior chamber.
D000818:Animals; D001082:Aqueous Humor / Q000187:drug effects / Q000502:physiology*; D002250:Carbon Radioisotopes; D003078:Colchicine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D011817:Rabbits; D011865:Radioisotope Dilution Technique
D002250:Carbon Radioisotopes; D003078:Colchicine