Figure 6.

Dependence of the force–calcium relationship on MgATP in the rat heart. (a) Decrease in Ca²⁺ sensitivity (increase in [Ca²⁺] at half-maximum) as [MgATP] increases from 30 to 100 µM ([Mg²⁺] = 50 µM). (b) Decrease in the maximum tension with increasing [MgATP]. Adapted from Best et al. (1977).