Expression of membrane-bound carbonic anhydrase isozyme XII in mouse and rat tissues

Background and aims: Carbonic anhydrase XII (CA XII) is a membrane-bound isozyme expressed in some normal human tissues, upregulated in some cancers, and is showed to be a hypoxia-inducible gene product. The expression of CA XII mRNA has been demonstrated in mouse kidney. This study concentrated on the research of the expression of CA XII in all mouse tissues, and later on in rat brain tissues. Methods: mRNA transcription was studied by PCR in mouse tissues and by reverse transcriptase-PCR (RT-PCR) in rat tissues. CA XII protein in mouse tissues was studied by Immunohistochemistry (biotin streptavidin complex method). The studies on rat brain tissues were made by in situ hybridization and northern blot methods after kainic acidinduced status epilepticus. In situ hybridization showed the location of the expression where as northern blot served as a measure of quantity of the expression. Results: CA XII mRNA is expressed in mouse kidney, brain, lung, testis and embryos. In embryos the expression became stronger with increasing age indicating developmental regulation. CA XII protein has a very limited expression distribution (mouse kidney and colon). In rat brain tissues CA XII mRNA is expressed mainly in dentate ganule cells, cortex and choroid plexus. Kainic acid stimulated the expression throughout the cortical layer. Conclusions: The high expression of CA XII in mouse kidney and colon suggests a role for CA XII in the maintenance of body ion and pH homeostasis in the mouse. Kainic acid stimulates CA XII expression throughout the cortical layer. The physiological significance of the observed cortical induction of CA XII remains obscure, but the high expression of CA XII in the choroid plexus suggests an analogous role for this membrane-bound isozyme. CA II is known to participate in CSF secretion.