Fig. 9. Relationship between SR Ca2+ loading and membrane potential in
control (filled circles) or with isoproterenol (ISO) + low extracellular
[Ca2+] (open circles). ISO + low [Ca2+] significantly
affected the relationship (P<0.001, N=5). Asterisks
denote a significant (P<0.001) difference between control and ISO
+ low [Ca2+].