Airway hyper-reactivity and eosinophilia in rats treated with Sephadex particles.

The intravenous injection of Sephadex particles (G200) into rats produced a specific increase in numbers of blood eosinophils, peaking 7 days later. A second injection, given on day 14 when the numbers of blood eosinophils had fallen to control levels, produced a dose-dependent increase in numbers, greater than the first, and peaking 5 days later. At this time, there was a dose-dependent increase in numbers of eosinophils, but not of other leucocytes, in broncho-alveolar lavage fluids and lung tissue, together with an increase in sensitivity of the rats to the respiratory effects produced by the intravenous injection of 5-hydroxytryptamine.