Imprinting, digoxin uptake and storage in Tetrahymena

Area of Science:

• Pharmacology
• Cell Biology
• Protozoology

Background:

• Digoxin is a cardiac glycoside with a narrow therapeutic index.
• Cellular imprinting, where cells retain a memory of prior drug exposure, has been observed in mammals.
• Tetrahymena are single-celled eukaryotes often used as model organisms.

Purpose of the Study:

• To investigate if Tetrahymena exhibit digoxin imprinting after drug exposure.
• To determine the duration of digoxin release into the culture medium.
• To explore the potential for Tetrahymena to produce digoxin-like substances.

Main Methods:

• Tetrahymena cultures were exposed to high concentrations of digoxin.
• Digoxin levels in the culture medium were measured over time after drug removal.
• Re-administration of digoxin was performed to assess cellular uptake.
• Radioimmunoassay (RIA) was used to detect digoxin-like substances.

Main Results:

• Tetrahymena released digoxin into the medium for up to three days post-exposure.
• Digoxin release subsided after nine to fifteen days.
• Re-exposure to digoxin led to increased digoxin consumption (storage) by Tetrahymena.
• Experiments suggest Tetrahymena may produce a digoxin-like substance detectable by RIA.

Conclusions:

• Tetrahymena exhibit digoxin imprinting, a phenomenon previously observed in mammals.
• The findings suggest Tetrahymena possess a mechanism for retaining drug memory.
• Tetrahymena may be capable of synthesizing endogenous digoxin-like compounds.