(A) In vivo measurements of resting [Ca2+]i and (B) resting [Na+]i before and after exposure to 2 vol% halothane. (C,D) In vivo measurements of resting [Ca2+]i and [Na+]i before and after exposure to 1.5 vol% isoflurane. In all cases, resting values of [Ca2+]i and [Na+]i were significantly increased at rest (P<0.001) and both rose after exposure to halothane or isoflurane (P<0.001). [Ca2+]i, intracellular calcium; [Na+]i, intracellular sodium; HALO, halothane; ISO, isoflurane; MHN, MH normal; MHS-Hom, homozygous MHS; MHS-Het, heterozygous MHS.