Lens and eye toxicity research最新文献

Ocular irritation includes a wide variety of mechanisms some of which can be explored by in vitro methods. For example, the effects on epithelial cells that constitute the outer layers of both the conjunctiva and the cornea may result in direct cytotoxicity or impairment of cellular functions -such as impermeability-, phenomena that can be explored in vitro. Irritancy may also involve inflammation of the conjunctival connective tissue and of the corneal stroma with its vascular and cellular features; effects on the stroma can lead to the opacification of the cornea; this last phenomenon may be the consequence of mechanisms such as modification of the structure of proteins or changes in stroma hydration which in particular is closely related to corneal endothelium metabolic activity. Recovery after eye injury depends partly on the extent of ocular damage and on the residual mitotic activity of the remaining cells. We have studied 41 surfactants, lotions and shampoos in 6 to 8 in vitro methods each one exploring one or two endpoints that could be linked to the ocular irritancy phenomena described above. In vivo ocular irritancy data for these materials from previous studies were compared to in vitro results. The results obtained show that -among the techniques that were investigated and for the categories of substances that were studied- the Het-CAM test and more particularly the endpoint that is related to vascular effects gives the best assessment of acute ocular irritancy (Spearman's rho coefficients between in vivo and in vitro data greater than 0.90); however, cell culture methods, especially one based on short contact time between cells and products and on evaluation of early toxic effects, also proved interesting (Spearman's rho coefficients between in vivo and in vitro data greater than 0.85). Moreover, the isolated cornea opacity and permeability test gave complementary information more related to recovery from surfactant-induced damage. These encouraging results lead us to consider in vitro ocular safety assessment with optimism for the categories of products investigated.

Incubation of whole bovine lens with 10(-7) M 12-O-tetradecanoylphorbol-13-acetate (TPA) led to the lens opacity within 24 h. The hydrogen peroxide (H2O2) concentration in the whole lens was elevated 4 fold after treatment with either 10(-7) M TPA or 2.5 mM glucose/20 microM glucose oxidase. The lens opacification and H2O2 elevation were TPA dose-dependent. Preincubation of the lens with anti-tumor promoting agents EGCG (epigallocatechin gallate) or Sarp A (sarcophytol A) stopped the TPA-mediated opacification process and suppressed H2O2 elevation.

A new adrenergic antagonist designed for topical use to induce pupillary miosis has been tested for direct toxicity on isolated rabbit corneal endothelium. Dapiprazole hydrochloride was perfused across endothelia in the specular microscope at concentrations from 1.25 micrograms/ml to 1000 micrograms/ml. No toxicity was observed, as determined by corneal thickness determinations over a 3 hour perfusion period, until concentrations greater than 125 micrograms/ml were reached. At 250 micrograms/ml a swelling rate of 17.8 microns/hour occurred, and at 500 micrograms/ml the swelling rate was 17.1 microns/hour; with 1000 micrograms/ml inducing a swelling rate of 23.3 microns/hour. It is evident that the drug concentration that reaches the endothelium after topical application has no toxic effect on the cornea, and that the drug should only be used as directed and not used as an anterior chamber perfusate.

We investigated the effects of perfluoro-n-octane liquid on the rabbit corneal endothelial permeability to inulin and dextran. Permeability measurements were made either after 10 minute in vitro exposure of the endothelium to 50 microliters of the test liquid or after one week exposure in vivo following injection of 50 microliters of the test fluid into the anterior chamber. Retention of the perfluorocarbon on the in vitro cornea and in the anterior chamber during the appropriate exposure time was visually verified. The corneal endothelial permeability was unchanged after either short or sub-chronic treatment with perfluoro-n-octane indicating an absence of toxicity for this substance should it reach the cornea either intraoperatively or postoperatively.

The background leading to the need for ocular toxicity testing is reviewed. Awareness of side effects of various categories of drugs (e.g., steroids and cataracts) has provided impetus for examination of many categories of compounds including ocular drugs, cosmetics and household chemicals. The standard test (Draize) used for many years in the evaluation of ocular toxicity of many chemicals is being modified or replaced by other procedures. Modifications include volume and/or concentration reductions. Replacements include the use of in vitro systems of either freshly isolated tissues, tissue cultured cells, or non-living systems. The relative predictability of each approach is evaluated with the conclusion that only in vivo testing (albeit using low doses and low volumes) can reflect the full spectrum of potential responses. Each in vitro methodology has at least one drawback relative to in vivo test procedures.

The intraocular concentration of fluconazole was measured in nonvitrectomized and vitrectomized eyes after an intravenous administration of 5 or 25 mg/kg fluconazole in albino rabbits. Respective fluconazole concentrations in the aqueous, vitreous and serum 1 hour after administration were 2.87, 1.72 and 4.60 micrograms/ml at 5 mg/kg administration, and 14.93, 7.05 and 20.63 micrograms/ml at 25 mg/kg administration, indicating high and dose-dependent intraocular penetration of fluconazole. Intraocular penetration of intravenously administered fluconazole was moderately, not very much, enhanced by vitrectomy. The in-vitro electroretinogram (ERG) remained unchanged after perfusion with 20 micrograms/ml of fluconazole. The in-vivo ERG and the visual evoked potential was unchanged after the daily administration of 25 mg/kg fluconazole for 8 days. The toxicity of fluconazole on the retina would be low and within safety limits so far as it is used at clinical dosage. Fluconazole may have a place in the treatment of fungal ocular infections.

To investigate the route of drug penetration into the eye and drug distribution patterns in the lens, the distribution of aldose reductase inhibitor (AL-04114) in the lens was measured in short term bovine lens organ cultures and topical administration to rabbit eyes. A micro lens sectioning technique was applied to determine drug localization within the lens. Freshly enucleated bovine lenses were incubated with different concentrations of an ARI (AL-04114)-containing medium for 3 hours. For the in vivo study, 40 microliters of 0.3% AL-04114 (ophthalmic solution) were administered into the cul de sacs of rabbits 3 times at 3 hour intervals. After the incubation and final instillation, the lenses were divided into an equatorial ring and several layered sections. Drug concentration was measured by a reversed-phase HPLC system. The drug concentration was highest within the layer of the posterior shallow cortex > equator > anterior shallow cortex. No drug penetration was observed in the anterior/posterior deeper cortex or nucleus in vitro. The in vivo experiment revealed drug penetration in the equator and anterior shallow cortex, but not in any other lens layers. Drug penetration was detected within the serum and aqueous humor, but not in the vitreous.