Pumps in Pathological Conditions

In hypertensive animals, altered Ca +-pump activity in vascular smooth muscle cells may contribute to the increase of blood pressure. In a previous review on altered Ca2+ metabolism in spontaneously hypertensive rats, we concluded that most of the results pointed to a diminished ER Ca + transport (Raey-maekers and Wuytack, 1993). Low et al. (1993b) came to the same conclusion using the inhibitor CPA as a tool, whereas new results from Levitsky et al. (1993) favor the opposite view. These authors found an increased ER function in the abdominal aorta of SHR rats and an elevated level of SERCA2 mRNA. 

The data on alterations of PM Ca + transport in hypertensive animals are conflicting, with some authors reporting a decrease and others an increase. An overview of these conflicting results is given by Mon-teith et al. (1994). 

Reactive oxygens, especially hydrogen peroxide, superoxide, and perhydroxyl radicals, have been implicated in a variety of pathophysiological conditions. In cardiac muscle, the Ca +-transport ATPase of the SR in particular is highly susceptible (Kukreja et al, 1988 Scherer and Deamer, 1986). The PM and especially the ER Ca + pumps of pig coronary artery are also susceptible to superoxide radicals (Grover and Samson, 1988, 

1989) and to hydrogen peroxide (Grover et al., 1992). The effect of superoxide is probably due to the irreversible modification of sulfhydryl groups (Scherer and Deamer, 1986 Suzuki and Ford, 1991). Also the vasoconstrictive side effect of alloxan has been ascribed to the formation of hydrogen peroxide and the subsequent inhibition of Ca + transport (Kwan and Beazley, 

Furukawa, K.-L, Tawada-Iwata, Y, and Shigekawa, M. (1989b). ]. Biochem. (Tokyo) 106, 1068-1073. 

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