The Forensics Mentors Institute

Back

The Search for Endogenous Digoxin-Like Compounds - William A. Dunn, M.S.

Digoxin like immunoreactive compounds (DLIF's) have been referenced in the literature for many years and accurate methods for the detection and quantitation of two of these (digoxin and digitoxin) of have been developed. However, it has been noted that certain patients not receiving these compounds can elicit a false positive reaction for digoxin or digitoxin by immunoassay as well as by the older method of 86Rb uptake inhibition.

Digoxin and digitoxin exert their effect in cardiac tissue through the inhibition of sodium-potassium ATPase (Na/K ATPase) by competing with potassium at its binding site. Many intracellular functions are effected by Na/K ATPase. Among these are the control of intracellular Calcium (Ca2+), phosphate (PO43-), aminoacids, glucose and pH. As a result of the action of Na/K ATPase, intracellular sodium increases and the resulting sodium gradient is decreased. In heart muscle, the net result is an increased amount of intracellular calcium available for contraction.

uring this seminar, evidence as to why Ouabain (Figure 1.) is one of these DLIF's as well as evidence that it is an endogenous compound that may cause a false positive reaction by immunoassay or 86Rb uptake inhibition will be presented . In addition, other compounds that are potential DLIFs will be discussed.

Figure 1.