The uptake of mepacrine by horse polymorphonuclear leucocytes in vitro.

The research investigates the absorption of mepacrine, a type of drug, by certain white blood cells in horses. This absorption was noted to happen in two stages, initially quick and mostly complete in the first 10 minutes, and then slower and ongoing after 60 minutes.

Research Methodology

• The study focused on the absorption of mepacrine by a specific type of white blood cell called polymorphonuclear leucocytes (PMN), found in horses.
• These cells were isolated, and the absorption of the drug was analytically measured using a method called spectrophotofluorimetry. This technique measures changes in light properties to infer the presence and concentration of substances.
• Mepacrine’s action inside the cells was visualized directly through fluorescence microscopy, a tool that highlights and illustrates specific components inside a cell.

Observations and Findings

• The researchers noticed two distinct phases of drug uptake. The first phase is characterized as the rapid uptake and was essentially complete by 10 minutes. The second phase was slower in comparison and continued even after 60 minutes.
• Fluorescence microscopy revealed the appearance of mepacrine inside the cells. The drug initially appeared as discrete yellow dots within 30 seconds, corresponding in size and number to the PMN cell granules.
• Following 5 minutes after introduction, mepacrine was also noticed around the cell nuclei, with the fluorescence in this area increasing over time.

Conclusions

• The researchers inferred from these observations that the absorption of the drug by the PMN cells happens at two distinct rates, with a quick uptake phase followed by a slower one.
• They concluded that the swift initial uptake represents the drug passing through the plasma (outer) membrane of the cell and into the cell’s granules.
• The slower, ongoing absorption could be indicative of the drug binding at the nuclear level.