Lipocortin I immunolocalization in normal and hydropic guinea pig ears

Annexins are a family of eight highly conserved proteins that bind phospholipids in the presence of calcium. One of these proteins, lipocortin I, has restricted distribution in adult and developing tissues, suggesting regulatory function. Among the protean roles theorized are regulation of inflammation by influencing eicosanoid production, participation in endo- and exocytosis, and control of membrane permeability. Such processes could have important roles in the inner ear; therefore, we investigated the patterns of lipocortin I expression in the normal guinea pig ear. Lipocortin I appeared at high levels in nonsensory, endolymph-facing tissues. Perilymph-facing cells had little lipocortin I activity. Lipocortin I was minimally expressed, or is absent, in sensory cells of the cochlea and vestibular systems. In the kidney, changes in quantity and distribution of lipocortin I have been seen during recovery from acute tubular necrosis. In an attempt to gain insight into the role of lipocortin I, the authors investigated its response to an experimental insult. Surgically created endolymphatic hydrops was chosen as an insult involving the endolymph-producing epithelia that richly express lipocortin I. Comparing unilaterally created hydrops, for up to 3 weeks' duration, to contralateral control ears demonstrated no quantitative or distribution changes in lipocortin I.