Cellular calcium metabolism

The addition of All to the target tissues under discussion leads to three changes in cellular calcium metabolism (1) a transient increase in cytosolic calcium (2) a reduction in total cell calcium and (3) a sustained increase in the rate of calcium influx across the plasma membrane. Each of these changes in cellular calcium metabolism is discussed below. 

Fig. 1. All-induced alterations in cellular calcium metabolism. Indicated are the increase in cytosolic calcium (upper left panel) enhanced calcium influx (upper right panel) the loss of total cell calcium (lower right panel) and the calculated compensatory increase in calcium efflux as a function of time after All addition (at arrow).

In addition to the well-known iron effects on peroxidative processes, there are also other mechanisms of iron-initiated free radical damage, one of them, the effect of iron ions on calcium metabolism. It has been shown that an increase in free cytosolic calcium may affect cellular redox balance. Stoyanovsky and Cederbaum [174] showed that in the presence of NADPH or ascorbic acid iron ions induced calcium release from liver microsomes. Calcium release occurred only under aerobic conditions and was inhibited by antioxidants Trolox C, glutathione, and ascorbate. It was suggested that the activation of calcium releasing channels by the redox cycling of iron ions may be an important factor in the stimulation of various hepatic disorders in humans with iron overload. 

Borle, A. B. Calcium metabolism at the cellular level. Fed. Proc. Fedn. Amer. Socs. exp. Biol. 32, 1944(1973)... 

The effects of berbamine on energy metabolism in isolated rat alveolar type II cells (cells which play a critical role in the maintenance of normal lung function) were studied. Incubation of type II cells with berbamine produced a reduction in cellular ATP content, but there was no effect of the alkaloid on cellular oxygen consumption. Berbamine produced an increase in internal calcium levels of type II cells, and incubation of the cells with calcium ionophore, 4-bromo A-23187, led to increased amounts of cellular calcium and reductions in ATP levels, with no effect on oxygen consumption. Exposure of isolated lung mitochondria to calcium produced a concentration-dependent reduction in ATP synthesis with no effect on mitochondrial oxygen... 

Cellular calcium kinetics and metabolic energy supply... 

A variety of lipid molecules take part in diverse aspects of metabolism and its control. Polyunsaturated fatty acids and their metabolites have been discussed above. Others are the fat-soluble vitamins, retinol (vitamin A) and tocopherol (vitamin E) (Chapters 5 and 8). Sterols, such as cholesterol, regulate membrane function and act as precursors for a range of molecules with diverse metabolic activities cholecalciferol (vitamin D), which is metabolized further to hydroxylated derivatives that regulate calcium metabolism and other aspects of cellular function (Chapters 5 and 7) bile acids, which are involved in lipid absorption (Chapters 4 and 7) and steroid hormones (Chapter 7). 

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