Expression of membrane-associated carbonic anhydrase isoforms IV, IX, XII, and XIV in the rabbit: induction of CA IV and IX during maturation

Abstract

Several carbonic anhydrase (CA) isoforms are associated with plasma membranes. It is probable that these enzymes interact with anion transporters to facilitate the movement of HCO3− into or out of the cell. A better knowledge of CA isoform expression in a given tissue would facilitate a systematic examination of any associations with such transporters. We examined the expression of CAs IV, IX, XII, and XIV mRNAs in rabbit tissues, including kidney, heart, lung, skeletal muscle, liver, pancreas, gall bladder, stomach, small intestine, colon, and spleen, using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). CA IV mRNA was mainly in kidney, heart, lung, colon, and gall bladder. CA IX mRNA was restricted to stomach, gall bladder, duodenum, and early jejunum. CA XII mRNA was found in kidney and colon. CA XIV mRNA was localized to heart, lung, skeletal muscle, and liver. The data indicate that there are different patterns of CA expression in various tissues: CA IX was expressed in the proximal gastrointestinal tract, whereas CA XII and CA IV were more distal. CA IV and CA XII are important kidney isoforms. CA XIV was abundant in metabolically active tissues such as liver, heart, lung, and skeletal muscle. Some significant species differences were noted in the expression of some of these isoforms; for example, CA XIV is not expressed in rabbit kidney, despite being abundant in mouse kidney. Maturational studies showed that the expression of CA IX mRNA and protein increased markedly with weaning (∼3–4 postnatal wk) and was well correlated with the maturational expression of the α-subunit of the gastric H+,K+-ATPase, suggesting that function of CA IX and the gastric H+ pump might be linked in the digestion of adult foodstuffs. The unique pattern of membrane-bound CA isoforms suggests different functional associations with transporters, depending on the physiological demands on the tissue.

The role of carbonic anhydrases in renal physiology

“…92 In contrast to mouse kidney, CAXIV is not abundantly expressed in human kidney 10 and CAXIV mRNA and protein are virtually undetectable in rabbit kidney cortex. 63 A complementary DNA sequence for a novel CA isoform, CAXV, was submitted to the NCBI in 2000 (GenBank s accession no. AF231122), and Hilvo et al 12 recently reported expression of CAXV mRNA in mouse tissues including kidney and brain.…”

“…22,101 CAIX is abundantly expressed in the proximal gastrointestinal tract including the stomach and gall bladder but not in normal kidney. 63,102,103 CAIX expression is also observed in the basolateral membrane of enterocytes of duodenum and jejunum, with most abundant expression occurring in the crypts in regions where epithelial cells exhibit high proliferative capacity. 102 The function of CAIX in the gastric mucosa has yet to be defined, but basolateral expression of CAIX suggests a role in facilitation of chloride/ bicarbonate exchange resulting in bicarbonate extrusion across the basolateral membrane of gastric parietal cells coupled with proton secretion by gastric H þ , K þ ATPase.…”

“…In a recent study we demonstrated that induction of CAIX during rabbit maturation coincided with upregulation of the H þ , K þ ATPase a-subunit,. 63 Thus, CAIX likely facilitates H þ / HCO 3 À transport in order to maintain cell pH in gastric and duodenal epithelium exposed to gastric acid in addition to facilitating bicarbonate extrusion in acid-secreting parietal cells.…”

Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes

“…1 Of the 15 known mammalian CAs, six are extracellular: CA IV, VI, IX, XII, XIV, and XV (reviewed in ref. 24). CA IX, XII, and XIV are integral membrane proteins with an extracellular enzyme domain that is continuous with a single transmembrane domain.…”

Mechanism of Cd-Induced Inhibition of Na-Glucose Cotransporter in Rabbit Proximal Tubule Cells: Roles of Luminal pH and Membrane-Bound Carbonic Anhydrase

“…These results suggest that inhibition of luminal membrane-bound CA is important in preventing Cd-MT-induced damage. Among the many isoforms of CA, CA IV, XII, XIV, and XV are membrane-associated and reported to be located in the kidney, while CA XIV is not detected in the rabbit, but is detected in the mouse kidney [16, 17]. …”