Knockdown of V-ATPase subunit A (alphatp6v1alpha) impairs acid secretion and ion balance in zebrafish Danio rerio

In the skin of zebrafish embryo, the vacuolar H(+)-ATPase (V-ATPase, H(+) pump) distributed mainly in the apical membrane of H(+)-pump rich cells, which pump internal acid out of the embryo and function similar to acid-secreting intercalated cells in mammalian kidney. In addition to acid excretion, the electrogenic H(+) efflux via the H(+)-ATPases in the gill apical membrane of freshwater fish was proposed to act as a driving force for Na(+) entry through the apical Na(+) channels. However, convincing molecular physiological evidence in vivo for this model is still lacking. In this study, we used morpholino-modified antisense oligo-nucleotides to knockdown the gene product of H(+)-ATPase subunit A (alphatp6v1alpha) and examined the phenotype of the mutants. The H(+)-ATP knockdown embryos revealed several abnormalities, including suppression of acid-secretion from skin, growth retardation, trunk deformation, and loss of internal Ca(2+) and Na(+). This finding reveals the critical role of H(+)-ATPase in embryonic acid-secretion and ion balance as well. Key words: H+-ATPase, morpholino-knockdown, acid/base regulation, Na+, Ca2+