Fig. 2. Characterization of V-ATPase expression and physiology. Whereas NaV1.5 (A,A') and most transporter genes tested, including Kir6.2 and subunits of the H⁺/K⁺-ATPase, are absent, both V-ATPase mRNA and protein are detected in the regeneration bud (B,B',C,C'). High magnification of section reveals the predicted cell-membrane localization for the protein (C''; scale similar to Fig. 1F''). (D) As in regenerating tails, amputation during the refractory period (st. 46) results in V-ATPase protein expression at 24 hpa. The same is true in irradiated larvae examined at 48 hpa (E), which exhibit no cell proliferation, as detected by the phosphorylated Histone H3B marker (F, compare with normal pattern of proliferation in G). Sections were generated as described by Levin (Levin, 2004). Larvae shown in A-E are oriented with anterior towards the bottom; sections A',B',C',F',G' are oriented with anterior to the right and dorsal upwards. Larvae in F,G are shown at 48 hpa. White arrowhead points to regeneration bud with lack of expression. Red arrows and arrowheads indicate positive signal (expression of RNA or protein marker).