We analysed the tissue plasminogen activator (TPA) content of the corneal epithelium, endothelium, and stroma and of the lens, as well as the aqueous and vitreous humors, in dog, calf, and monkey eyes. A quantitative estimation of the TPA activity in the corneal tissues by the [125I]fibrin-coated well assay showed similar levels of activity in the corneal epithelium, stroma, and endothelium. However, some differences were observed among the three mammalian species analysed. The values, expressed in urokinase (UK) units of activity per mg protein, ranged from 0.8 +/- 0.22 to 1.03 +/- 0.23 for the epithelium, 0.47 +/- 0.13 to 0.98 +/- 0.2 for the stroma, and 0.48 +/- 0.11 to 0.93 +/- 0.22 for the endothelium. The lens, the vitreous and the aqueous humor yielded low to negligible values. However, by using the enzyme-linked immunosorbent assay (ELISA) method, we detected an appreciable amount of TPA in the lens (9.49 +/- 1.5 ng TPA per ml lens), corneal epithelium (1.43 +/- 0.29 ng TPA per mg protein) and vitreous humor of the dog (5.71 +/- 0.61 ng TPA per ml vitreous humor) and of the calf (5.7 +/- 0.44 ng TPA per ml vitreous humor). Such discrepancies may reflect species-specific variation in the TPA content of the tissues and possibly the limitations of the techniques utilized, because of the problem related to cross-reactivity between the TPA of a given species and the antibody used in the assays.(ABSTRACT TRUNCATED AT 250 WORDS)