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Marc Yonkers, Sarah Farukhi, James Hall; Hormonal modulation of Aquaporin-1 function in Xenopus oocytes: a model for idiopathic intracranial hypertension. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5105.
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Idiopathic Intracranial Hypertension (IIH) is a disorder primarily affecting obese women of childbearing age and can lead to permanent loss of vision. The underlying mechanism of rises in intracranial pressure is unknown, however increased systemic estrogen and glucocorticoid concentrations are risk factors. We aim to test the effects of estrogen and glucocorticoid on Aquaporin-1 (AQP1) channel function, one of two aquaporins that facilitate water transport in cerebrospinal fluid (CSF). Prior studies demonstrate AQP1 knockout mice display a 5-fold reduction in CSF pressure, suggesting AQP1 function contributes to CSF pressure. Here we describe a model to test AQP1 function in the xenopus oocyte, which provides an assay to determine hormonal effects on AQP1 function.
AQP1 cRNA was injected into xenopus oocytes and channel function was assessed with a swelling assay. In ND96 hypotonic solution, xenopus oocytes were assessed for increase in cross sectional area over time indicating increased permeability over a 48 hour incubation period. Oocyte area was measured in a range of physiologic estrogen doses, added externally, and compared to control oocytes exposed to vehicle solution.
Oocytes injected with AQP1 cRNA swelled faster than control oocytes exposed to the same hypotonic solution. The permeability rate of AQP1 injected oocytes was 4-fold the permeability rate of control oocytes (P < 0.05).
The increased permeability in oocytes injected with AQP1 cRNA, when compared to control oocytes, demonstrates the functionality of the AQP1 channels in the oocyte membrane. The functional AQP1 demonstrates the xenopus oocyte’s ability to successfully translate AQP1 cRNA and integrate AQP1 protein. This establishes the framework for further investigation regarding the role of estrogen in the pre and post-translational stages of AQP1.
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