Radiolabeling of equine platelets in plasma with 111In-(2-mercaptopyridine-N-oxide) and their in vivo survival.

This study presents a method for isolating and labeling horse platelets with the radioactive isotope indium 111 in order to track them. The research found effective results with intravascular survival times of the labeled platelets ranging between 3.5 and 5.5 days in healthy horses.

Isolation and Radiolabeling Method

• The researchers have developed a new method for the in vitro isolation and radiolabeling of horse platelets.
• This technique utilizes the isotope indium 111 (111In), which has a half-life of 2.8 days and emits gamma radiation at certain energy levels.
• The process involves complexing 111In with the lipid-soluble chelating agent, 2-mercaptopyridine-N-oxide (merc), in a water-based medium to achieve radiolabeling. This agent helps to securely bind the radioisotope to the platelets for accurate tracking.

Labeling Efficiency in Different Conditions

• The study assesses labeling efficiency in two different cases: when autologous plasma is pretreated with ferric citrate and when it is not.
• Pretreatment with ferric citrate significantly enhances efficiency, with the labeling efficiency being 82% in its presence as opposed to only 24% in its absence.

Intravascular Survival of Radiolabeled Platelets

• The survival rates of the labeled platelets within the vessels were also evaluated.
• The researchers used different models of assessment including simple linear, exponential, mean, weighted-mean residual sum of squares analysis, and multiple-hit model.
• In the healthy horses studied, the mean intravascular survivals of indium 111-labeled platelets varied from 3.5 to 5.5 days depending on the model of assessment used.

Significance of the Study

• The presented in vitro radiolabeling and isolation method may serve to improve our knowledge about platelet functionalities and lifecycles in equines.
• This could open up exciting possibilities for studying platelet behavior, diseases, and therapeutic responses in not just horses but potentially other species as well.