Plasma factors affecting enzyme levels

Factors Affecting Enzyme Levels in Plasma or Serum ... 

Lipid transport mechanisms exist that shuttle cholesterol and triglycerides among the liver, intestine, and other tissues. Normally, plasma lipids, including lipoprotein cholesterol, are cycled into and out of plasma and do not cause extensive accumulation of dcpo.sits in the walls of arteries. Genetic factors and changes in hormone levels affect lipid transport by altering enzyme concentrations and apoprotein content, as well us the number and activity of lipoprotein receptors. This complex relationship makes the treatment of all hyperlipoproteinemias by a singular approach difficult, if not impractical. 

The use of appropriate normal ranges is important in evaluating abnormal levels of plasma enzymes. However, an abnormal isoenzyme pattern may occur despite normal total activity (see above). The standard unit for enzyme activity was discussed in Chapter 6. The normal range is affected by a variety of factors age, sex, race, degree of obesity, pregnancy, alcohol or other drug consumption. 

The rates and routes of metabolism can vary with age and the lower rates and reduced routes of metabolism usually seen in the yoimg and the old can make them more susceptible to drug action. Differences in hormonal levels, in particular, can lead to differences in metabolism between sexes. Dietary and environmental factors such as the presence of alcohol and cigarette smoke can affect metabolism, as can certain disease conditions, e.g., liver disorders, diabetes. Such conditions can lead to decreased enzyme activity, altered hepatic blood flow, and changes in plasma protein levels which, in turn, can affect circulating active drug levels. 

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