Hormonal control of neutrophil chemotactic activity in the rat vagina

A sexual-hormone-dependent neutrophil chemotactic factor(s), operative under physiological conditions, is described. Rat vaginal washouts were shown to be both chemotactic and chemokinetic for rat neutrophils in vitro, whereas macrophages were not attracted. Peak activity was observed at the end of estrus and preceded maximal neutrophil infiltration in the vagina. In order to mimic these events, gonadectomized animals were treated with estradiol for a week. They showed a similar peak of chemotactic activity 30-36 h after estradiol withdrawal, accompanied by a massive neutrophil accumulation. These data suggest that a decrease in estradiol level permits the expression of the chemotactic signal. There was no evidence for chemotaxis and/or migration inhibitors before and during estrus or during long-term estradiol treatment of gonadectomized rats. Induced neutrophil accumulation in the peritoneal cavity and chemotactic responsiveness of these cells in vitro were similar in all stages during the estrus cycle. Estradiol, progesterone, testosterone, and hydrocortisone neither promoted nor significantly inhibited the neutrophil migratory behavior over a wide range of concentrations. Our experiments suggest that the periodic neutrophil accumulation in the rat vagina after estrus is triggered by locally expressed chemotactic mechanisms that are controlled by sexual hormones. The data provide the first evidence that hormonal changes can control chemotactic factors and thus indirectly control cell migration.