CARBONIC ANHYDRASE-II MESSENGER-RNA IS INDUCED IN RABBIT KIDNEY CORTEX DURING CHRONIC METABOLIC-ACIDOSIS

Carbonic anhydrase II (CA II), the predominant isoform of carbonic anh ydrase in the kidney, is believed to be localized primarily in the cyt oplasm of Proximal tubule and collecting duct intercalated cells. Carb onic anhydrase facilitates H+ secretion by catalyzing the formation of HCO3- from OH- in the presence of CO2. We have shown that renal corti cal CA II activity is stimulated during 4-6 days of chronic metabolic acidosis [L. P. Brion, B. J. Zavilowitz, O. Rosen, and G. J. Schwartz. Am. J. Physiol. 261 (Regulatory Integrative Comp. Physiol. 30): R1204 -R1213, 1991]. The purpose of these studies was to examine under simil ar conditions the regulation of CA II mRNA. We obtained a major portio n of the rabbit CA II cDNA by reverse transcription of total RNA from rabbit kidney followed by amplification using oligonucleotide primers prepared from conserved areas in the coding regions of human, mouse, a nd chick CA II cDNAs in a polymerase chain reaction (RT-PCR). The 696- bp RT-PCR product was sequenced and found to be 71-86% homologous to C A II cDNAs from the other three species. The deduced amino acid sequen ce agreed closely (>97%) with a previous Edman analysis of rabbit eryt hrocyte CA 11. Northern analysis showed expression of a approximately 1.4 kb RNA, with cortex > outer medulla > inner medulla. Steady-state mRNA expression from kidney cortex of acid-treated rabbits was about t wice that from controls, when normalized to the expression of beta-act in or malate dehydrogenase. The stimulation of CA II mRNA was greater after 3 days than after 5-6 days of acid treatment. Thus, during chron ic metabolic acidosis, there is an induction of CA II mRNA, which prec edes the increase in activity, indicating a possible role for this enz yme in the renal adaptation to this pathological state.