Correlation between blood eosinophilia and airways hyper-responsiveness in rats.

The injection of Sephadex particles intravenously into rats produced a specific blood eosinophilia and an hyper-responsiveness of the airways to 5-hydroxytryptamine (5-HT). The rats given Sephadex had an hyper-sensitivity to the respiratory effects of 5-HT in vivo with a shift to the left of the intravenous dose response curve. In vitro lung strips from rats given Sephadex were hyper-reactive to 5-HT in that the strips from these rats and control rats responded over the same dose range of 5-HT but the slope of the dose response curve and the maximum response were greater in the strips from the Sephadex treated rats. The levels of hyper-sensitivity in vivo and of hyper-reactivity in vitro both correlated with the numbers of blood eosinophils.