Temporary impairment of Müller cell metabolism in the rat retina by intravitreal injection of fluorocitrate.

Fluorocitrate was injected in the vitreum of rats in order to define the experimental conditions for a temporary impairment of Müller cell metabolism in the retina. Injection of 16 nmol of fluorocitrate appeared to fulfil this requirement since this dose resulted in a large decrease in retinal endogenous glutamine and a smaller decrease in glutamate within 6 hr of administration. The reversible nature of the effect was attested by a substantial recovery of the retinal levels of the two amino acids within 24 hr of injection. In vitro experiments of carbon incorporation from different substrates, carried out with retinas dissected from eyes previously injected with fluorocitrate, were consistent with a metabolic impairment of glial cells, since carbon incorporation from [14C]acetate into glutamine was almost completely abolished in the fluorocitrate-treated retinas. Electron microscopic examination in fluorocitrate-poisoned retinas demonstrated essentially selective ultrastructural alterations of Müller cells at times corresponding to their maximal metabolic impairment. Since Müller cells are by far the largest glial population of the rat retina, common astrocytes being only scattered in the nerve fibre layer, the present experimental model may be used to study the role of Müller cells in the metabolism of retinal neurotransmitters.