Intravascular neutrophilic granulocyte kinetics in horses.

This study investigates the behavior and life cycle of neutrophilic granulocytes, a type of white blood cell, in healthy horses. Granulocytes were tracked using a chromium-51 label and the data obtained was used to estimate the granulocyte population and turnover rate in the blood.

Granulocyte Tracking

The researchers performed a granulocyte kinetics study on four healthy horses. This involved:

• Using chromium-51 as a cell label to track the movement and behavior of granulocytes within the horse’s blood vessels.
• Measuring the disappearance rate of the labeled granulocytes which followed an exponential function.

Granulocyte Pool Estimation

The researchers estimated the total volume of granulocytes in the blood (total granulocyte pool). Using this value they found that:

• The average (mean) granulocyte count was 5.65 +/- 1.514 X 10(8) granulocytes per kg of body weight. This represents the total population of granulocytes in the horse’s blood, including those freely circulating and those attached (marginated) along the blood vessel walls.
• The average number of granulocytes freely circulating was 2.71 +/- 0.715 X 10(8) granulocytes per kg.
• Those marginated along blood vessel walls amounted to an average of 2.94 +/- 0.876 X 10(8) granulocytes per kg.

Granulocyte Life Cycle

The researchers studied the life cycle of the granulocytes in terms of their disappearance half-life and turnover rate. They found that:

• The average disappearance half-life (T1/2), or the time it takes for half of the granulocytes to disappear from the blood, was 10.5 +/- 1.33 hours.
• The mean granulocyte turnover rate, or the rate at which granulocytes are produced and destroyed, was 8.84 +/- 1.495 X 10(8) granulocytes per kg per day.

Impact of Recent Infections on Granulocyte Kinetics

Lastly, one of the horses that recently recovered from an infection showed increased granulocyte kinetics measurements. This underscores the role of granulocytes in immune response and suggests that their numbers may increase following an infection as part of the body’s defense mechanism.