Effect of estradiol and progesterone on antistaphylococcal activity of neutrophils from ovariectomized mares.

This research article investigates the effect of two hormones, estradiol and progesterone, on the bacteria-killing function of neutrophils in female horses that have had their ovaries removed and found no appreciable impact.

Study Overview

The study worked with neutrophils, a type of white blood cell known for their role in immune responses, extracted from the blood of mares who had undergone ovary removal. The researchers were interested in observing the effects that estradiol (a form of estrogen) and progesterone (another sex hormone), might have on the bactericidal, or bacteria-killing, properties that these neutrophils possess, particularly against the bacteria Staphylococcus aureus.

Methods

The researchers carried out two experiments:

• In the first experiment, neutrophils that had been sourced from four mares were subjected to a bactericidal assay, or test, incorporating either estradiol or progesterone.
• In the second experiment, three of the original four mares were given an intramuscular injection of estradiol daily for three consecutive days. Following this, 18 days after the initial injection of estradiol, the mares were given 300 mg of progesterone, also intramuscularly, for a period of six days. The bactericidal activity of the neutrophils, once again against Staphylococcus aureus, was tested on three occasions: four days after the first estradiol injection, 17 days post the first estradiol injection – which served as a control – and finally seven days after the first progesterone injection.

Measurements

The researchers measured the bactericidal activity of the neutrophils 30 and 120 minutes after their exposure to bacteria by counting the surviving bacteria using a method known as colony-forming units.

Results

The experiments found that both the presence of estradiol and progesterone and the supplementary administration of these hormones in the ovariectomized mares did not significantly alter the neutrophils’ ability to kill Staphylococcus aureus bacteria. These results suggest that the two hormones do not have a significant influence on neutrophils’ bactericidal activity in mares that have undergone ovary removal.