Serum lactate dehydrogenase isoenzyme 1 (LDH 1) in a patient with seminoma.

Lysozyme, a cationic protein, is found in biological fluids such as saliva both in the free form and associated with anionic proteins and polysaccharides to form reversible complexes. The degree of complexing depends on the concentration of these constituents, pH, and storage time, as well as other factors (2-6). Thus all our acid-treated samples gave higher values. Accurate determination of lysozyme in biological fluids should therefore take these variables into consideration. In this investigation we determined unbound and released lysozyme in parotid fluid samples of normal donors under standardized experimental conditions: acidification, which released the bound lysozyme; centrifugation, which eliminated the proteins present; and neutralization of the supernatant fluid to the original pH of the parotid saliva. This standardized procedure can be used for studying alterations in the concentration of lysozyme in parotid saliva that may be caused by various exogenous and endogenous factors or conditions such as eating, drinking, or smoking before sample collection; inflammation or infection in the oral cavity; and hormonal variations and systemic diseases. Thus the role of lysozyme in parotid saliva can be better understood.