Prostaglandin E₂ and the bovine sphincter pupillae

Abstract

Summary1. The bovine isolated sphincter pupillae incubated in Krebs solution releases a biologically active substance tentatively identified as prostaglandin E2. 2. The prostaglandin did not appear to be of neural origin or to result merely from tissue degeneration.3. The spontaneous release of prostaglandin E,-like material was related to the tone of the sphincter. Output increased as tone was acquired after setting up the tissue and fell when various procedures were used to reduce the tone. 4. Low concentrations of E and F-type prostaglandins produced slow, wellsustained contractions of the atonic sphincter, prostaglandin E2 being the most potent of those tested. The responses to prostaglandin EB were antagonized selectively by a prostaglandin antagonist SC-19220 (a dibenzoxazepine derivative) which in higher concentrations caused dose-dependent relaxations of the preparation. 5. Prostaglandins did not appear to modulate transmission from nerve to muscle in the sphincter. 6. The hypothesis that prostaglandin E2 might be produced to act as a local hormone causing tonic contraction of the sphincter pupillae is discussed.

Prostaglandin E2 and gastric acid secretion in man

“…An effect on acid secretion seems somewhat unlikely, but a hypothesis, apart from others such as the back-diffusion of hydrogen ions through a damaged mucosa (Davenport, 1965), is that PG release has a vasodilator role in gastric blood vessels (Eckenfels & Vane, 1972). PGs seem to generate muscle tone in some tissues which are contracted by PGE compounds (Posner, 1971;Bennett & Posner, 1971;Ferreira, Herman & Vane, 1972), and since PGE and A compounds produce vasodilatation, an inhibitory role is possible in blood vessels. Work on the kidney provides direct evidence for this view (McGiff, Crowshaw, Terragno, Lonigro, Strand, Williamson, Lee & Ng, 1970;Aiken & Vane, 1971), and the cerebral and conjunctional vasoconstriction produced by indomethacin provides indirect evidence (Sicuteri, Michelacci, Anselmi, 1965;Vecchio & Fontana, 1965).…”

Prostaglandin E receptor subtypes in smooth muscle: agonist activities of stable prostacyclin analogues

“…The bullock iris sphincter preparation contains a PGE-sensitive contractile system which is blocked by SC 19220 (Posner, 1973). Our recent studies (Dong & Jones, 1982) have revealed that iloprost, a stable and potent mimetic of PGI2 (Casals-Stenzel et al, 1983) (Figure 1), possesses remarkably high agonist activity on the iris preparation and appears to behave as a partial agonist at the PGE receptor.…”

Effects of Prostaglandins and Thromboxane Analogues on Bullock and Dog Iris Sphincter Preparations

“…In contrast the bullock iris sphincter is more responsive to PGE2 than PGF2. (Posner, 1973). We decided to characterize further the PGE-sensitive system in the bovine iris sphincter, with a view to comparing it with other smooth muscle preparations responsive to PGE2 and related analogues.…”