Measurement of adenosine concentration in aqueous and vitreous.

PURPOSE: The release of adenosine by the ischemic retina may be an initial signal in the development of ischemic macular edema and neovascularization. The levels of adenosine have never been quantified in ocular fluids. In this study, a technique was developed for in vivo measurement of the concentration of adenosine in aqueous and vitreous. METHODS: Aqueous and vitreous samples were obtained from bovine eyes after death and from live porcine eyes with the subject under general anesthesia. Samples from live eyes were immediately incubated in the sampling syringe with pentoxifylline, erythro-9-(2-hydroxy-3-nonyl) adenine, and dipyridamole to prevent synthesis or degradation of adenosine during the collection procedure, filtered, and flash-frozen in liquid nitrogen. All samples were then filtered and purified on phenylboronate agarose columns and incubated with chloroacetaldehyde to convert the adenosine present in the sample to the fluorescent derivative 1,N6-ethenoadenosine. The 1,N6-ethenoadenosine was separated by high-pressure liquid chromatography and then measured by fluorometry. RESULTS: Levels of adenosine as low as 0.5 pmole could be detected with this procedure, compared with 20 pmoles by UV detection. By using this technique to measure adenosine levels in the eyes of normal weanling domestic pigs, it was determined that the adenosine concentration in the aqueous was 321.3 +/- 164.9 nM and in the vitreous was 210.8 +/- 41.5 nM. CONCLUSIONS: The conversion of adenine-containing compounds to fluorescent 1,N6-etheno derivatives offers analytical advantages of selectivity and sensitivity for the quantitative determination of these compounds, with the fluorometric detection providing substantially greater sensitivity than direct detection by UV absorption. The levels obtained in vivo from anesthetized but otherwise healthy pigs presumably reflected basal aqueous and vitreous adenosine levels under the described conditions. This method should be useful in investigating more directly the role of adenosine in models of retinal or ocular ischemia in vivo and in measuring adenosine levels in vitreous or aqueous samples from human patients.

White-centered retinal hemorrhages as an early sign of preeclampsia.

PURPOSE/METHOD: We examined a pregnant patient who had symptomatic white-centered retinal hemorrhages. Severe preeclampsia rapidly developed despite the patient not having hypertension, proteinuria, or edema at initial examination. RESULTS/CONCLUSIONS: Retinal hemorrhages gradually resolved without treatment and visual acuity returned to 20/20 six months after emergency delivery of a healthy infant. Retinal or choroidal vascular abnormalities in pregnant patients may be caused by early preeclampsia and immediate obstetric referral is indicated.