The effects of prostaglandins on the intraocular pressure of the rabbit

Abstract

1. The effects of intracameral injections of prostaglandins E1, E2, Fia, F2a, and A1 were studied on.the intraocular pressure (IOP) of rabbits anaesthetized with urethane.2. With the exception of prostaglandin F,a, all the prostaglandins studied were found to be capable of producing a large, sustained rise in IOP, accompanied in many cases by miosis. 3. A marked decrease in response to repeated injections was found with all the prostaglandins studied; this effect was more pronounced following a large initial response to the prostaglandin. 4. The descending order of potency in their ability to raise IOP was as follows: prostaglandin Ei-E2>F2a>Al>Fia.5. Intracameral injections of prostaglandins E1 and E2 resulted in an increase in the protein content of the aqueous humour, which was related to the magnitude of the sustained increase in IOP. 6. Stabilization of the blood-aqueous barrier with polyphloretin phosgphate markedly reduced both the IOP response and the effect of prostaglandin E2 on the protein content of the aqueous humour. 7. It is concluded that the production of local vasodilatation and increased permeability of the blood-aqueous barrier play an important part in the effect of prostaglandins on the IOP. The involvement of prostaglandins in the response of the rabbit eye to irritation is discussed.Injections of prostaglandins into rabbit eyes have been shown by Waitzman & King (1967) to produce a sustained rise in intraocular pressure (IOP). This effect on the IOP was thought to result from an action of prostaglandins on the metabolic processes involved in aqueous humour production, rather than from vascular or permeaibility changes (Waitzman, 1968), although it was well known that many prostaglandins are powerful vasodilators. Moreover, it had been shown earlier that the response of the rabbit eye to irritation is associated with the release into the aqueous humour of irin, an ether-soluble spasmogen with vasodilator activity consisting of unsaturated hydroxy fatty acid(s)

Antagonism of some smooth muscle actions of prostaglandins by polyphloretin phosphate

“…Since irins, that is, prostaglandins, were shown to be involved in the response of the rabbit eye to irritation (Ambache, Kavanagh & Whiting, 1965;Ambache, Brummer, Rose & Whiting, 1966), the interaction of PPP with prostaglandin E2 (PGE2) was studied on rabbit intraocular pressure. PPP was found to antagonize the rise in intraocular pressure produced by intracameral injections of PGE2 (Beitch & Eakins, 1969). Following this observation , in a preliminary study, found that PPP selectively antagonized the smooth muscle stimulating actions of prostaglandins Fla (PGFla) and F2, (PGF2a) on the jird colon.…”

Prostaglandin-like Activity in Ocular Inflammation

“…Further examination of the prostaglandin-like activityfor example, by thin-layer chromatography-was not possible because of the small volumes available from each patient and the difficulty of obtaining these samples. Introduction Prostaglandins are present in ocular tissues (Ambache and Brummer, 1968) and can induce some of the characteristic changes associated with ocular inflammation, such as vasodilatation, increased vascular permeability, and a raised intraocular pressure (Beitch and Eakins, 1969;Eakins, 1970;Kelly and Starr, 1971;Starr, 1971).…”

Prostaglandins in Pyometrial Fluid From the Cow, Bitch and Ferret

“…In guinea-pigs and rats the uterus synthesizes mainly prostaglandin F2. Williams, Sneddon & Harney, 1974) Pyometrial fluid from the cow and bitch was not lacking prostaglandin E2, though the stimulus of prostaglandin production appeared incapable of directing synthesis towards producing predominantly prostaglandin E2, the 'active' prostaglandin in inflammation (Beitch & Eakins, 1969;Crunkhorn & Willis, 1971). This is in contrast to the sheep where, under experimental physiological conditions, a sterile fluid containing only prostaglandin F2.…”