The effect of vitreous humour on prostaglandin production by cultured rabbit chorioretinal fibroblasts

Abstract

Factors in vitreous humour which regulate prostaglandin production were investigated using cultured rabbit chorioretinal fibroblasts. These cells produced predominantly prostaglandin E 2, 6-ketoprostaglandin F 1α, a compound likely to be a metabolite of prostaglandin E 2 and 5-hydroxyeicosatetraenoic acid. The synthesis of 6-ketoprostaglandin F 1α was nearly completely inhibited by the cycloxygenase inhibitor aspirin and partially inhibited by 10 −6 M dexamethasone (49%) and 10 −5 M forskolin (68%). Addition of 10% rabbit vitreous humour to subconfluent cells maintained in Dulbecco's modified Eagle's medium plus 1% fetal bovine serum resulted in stimulation of 6-ketoprostaglandin F 1α production by as much as 246% as measured by radioimmunoassay. Chorioretinal fibroblasts labelled by [ 3H]arachidonic acid incorporation into cellular phospholipids synthesised greater amounts of all labelled arachidonic acid metabolites in response to vitreous humour. It was concluded, therefore, that there are factors present in vitreous humour of molecular weight above 10 kDa which are capable of stimulating cellular cycloxygenase activity. Confluent cells also responded to a factor(s) present in vitreous humour. The fraction of less than 10 kDa inhibited 6-ketoprostaglandin F 1α production by 50% when used at a concentration of 10%. Furthermore, 6-ketoprostaglandin F 1α production in confluent cells (but not subconfluent cells) was inhibited to 40% of control levels by vitamin C at a concentration of 1 mg 100 ml . The latter result points to an inhibitory role for vitamin C in vitreous humour. We conclude, therefore, that vitreous humour contains factors important for the regulation of prostaglandin metabolism in the eye.