Inhibition by derivatives of phloretin of anaphylactic histamine release from human lung tissue and of prostaglandin F2alpha-induced bronchoconstriction.

Derivatives of phloretin (25-1,000 mug/ml) among them polyphloretin phosphate (PPP), inhibited in a dose-dependent manner anaphylactic (birch pollen or horse dander) histamine release from human lung tissue passively sensitized with reaginic serum. Pretreatment with PPP of lung tissue sensitized both to birch pollen and horse dander counteracted to a similar extent the release of histamine induced by either allergen administered in sequence. The phloretin derivatives also antagonized the constrictor action of prostaglandin F2alpha on isolated human bronchi at concentrations which did not impair the responses to histamine. The low and high molecular weight derivatives of phloretin were comparably active on a weight basis in both experimental systems.