This graphic method can determine both the inhibition constant (K_i) and the type of inhibition [32]; V = maximal velocity, v = initial velocity, and K_i represents the inhibitor constant. Isolated hepatic microsomes were incubated with the indicated FFA and then influx activity measured as described in ‘Materials and methods’ section. The concentration of the FFA ranged from 0 to 100 μM, whereas free calcium was from 1 to 100 μM. The quotient velocity plots were generated based on the fact that ER Ca²⁺ uptake occurs primarily through an embedded membrane enzyme, calcium ATPase. Using this type of plot, the intersection of the lines represents the K_i (approximately 40 μM). Of note, this value is very close to the calcium uptake inhibition (IC₅₀) by DHA and ARA as depicted in Figure 2.