Proceedings of The Physiological Society

University of Oxford (2011) Proc Physiol Soc 23, C32

Oral Communications

Decreased abundance of proteins involved in cerebrospinal fluid production in slc4a10 knockout mice

H. H. Damkier1, J. Praetorius1

1. The Water and Salt Research Center, Dept of Anatomy, Aarhus University, Aarhus C, Denmark.

Deletion of the Na+ dependent Cl-/HCO3- exchanger slc4a10 from mice has been shown to cause a shift in the membrane localization of the Na+/H+ exchanger from luminal to basolateral in the choroid plexus (CP). No other acid/base transporters showed changes in localization or abundance (1). In addition to pH regulation, slc4a10 is believed to be the bottleneck for Na+ import from the blood side to the CP cell and thereby for the cerebrospinal fluid (CSF) production as such; slc4a10 knockout mice have decreased brain ventricles indicating decreased CSF secretion(2). The aquaporin 1 (AQP1) knockout mouse has decreased brain ventricle size and CSF secretion rate (3). Here, we investigate whether deletion of slc4a10 causes changes in abundance of AQP1 and Na, K ATPase in the choroid plexus as examples of prominent proteins involved in CSF secretion. Slc4a10 and AQP1 knockout mice, and wildtype littermates, were anaesthetized using isoflurane inhalation (3-4% in oxygen) and perfusion fixed through the heart using paraformaldehyde. Following dehydration, brain tissue was paraffin embedded and sections were cut using a rotary microtome. Protein abundances in the CP were semi-quantified from the immunofluorescence intensities of confocal micrographs. Images were acquired in the focal plane with the highest signal intensity using fixed instrument settings. Fluorescense intensities were compared using the unpaired t-test. The Na, K ATPase abundance was decreased by 36.4% (n=4, p=0.02 using ) and AQP1 was decreased by 42.7% (n=4, p=0.02) in the choroid plexus of slc4a10 knockout mice compared to wildtype littermates. Similarly we investigated the abundance of slc4a10 and Na,K ATPase in the choroid plexus of the AQP1 knockout mouse; a mouse with a similar choroid plexus phenotype. In the AQP1 knockout mice we find no difference in relative immunofluorescence intensity for slc4a10 (AQP1 wildtype 100± 10%, AQP1 knockout 73 ± 11%, n=5, p=0.12) or Na, K ATPase (AQP1 wildtype 100±19%, AQP1 knockout 158±32%, n=5, p=0.15). Thus, the cells of the CP seem to compensate for the loss of slc4a10 by decreasing the abundance of the molecular machinery involved in CSF secretion in response to the removal of the main basolateral Na+ loader. On the other hand, the removal of an important water channel in the AQP1 knockout mouse, with a comparable phenotype, does not seem to cause similar restructuring in the choroid plexus. This substantiates the previous study in the slc4a10 knockout mouse indicating that CP cells favor cell survival over CSF secretion and that slc4a10, but not AQP1, is perhaps more important for the survival.

Where applicable, experiments conform with Society ethical requirements