Pump by Hormones and Other Signals

It should also be mentioned that several groups have reported on the inhibition by IP3 of the PM Ca + pump in coronary artery smooth muscle (Popescu et al., 1986), cardiac muscle (Kuo and Tsang, 1988), and erythrocytes (Davis etal, 1991). In search for a possible mechanism of this effect, it was found that IP3 inhibits calmodulin binding to the red cell membranes (Davis etal., 1991). 

Ca2+-transport ATPases [PMCA (Niggli et al., 1982) as well as SERCA (Martonosi et al., 1985)] operate as obligatory Ca2+-H+ exchangers. Since the number of protons exchanged for Ca + has not been firmly es- 

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