Nonfunctional plasma enzymes

Plasma also contains numerous other enzymes that perform no known physiologic function in blood. These apparently nonfunctional plasma enzymes arise from the routine normal destruction of erythrocytes, leukocytes, and other cells. Tissue damage or necrosis resulting from injury or disease is generally accompanied by increases in the levels of several nonfunctional plasma enzymes. Table 7-2 lists several enzymes used in diagnostic enzymology. 

Potential limitations include the tendency for primary cells in culture to dedifferentiate and lose functional expression of enzymes and membrane transporters during the course of culture. For example, expression of enzymes important for drug metabolism, such as CYPs, tends to readily decrease if culture conditions are not optimized. Plasma membrane transporters, such as many of the OATs, can readily internalize and become nonfunctional dining the course of cultme (Lash et al, 2006). Our strategy to counteract these potential problems has been to use the serum-free, hormonally defined medium that has become standard with primary culture of epithelial cells and then add other supplements to optimize maintenance of differentiated fnnction (Lash et al., 1995 Lash, 2012). 

---