The generation of prostaglandins by human lung and their effects on airway function in man

Human dispersed lung cells containing 5-10% mast cells synthesised and released large quantities of prostaglandin D2 (PGD2) and thromboxane B2 (TXB2), with either IgE-dependent activation or ionophore A23187 challenge. The generation of these prostanoids and the release of histamine was related to the strength of activation stimulus. After activation the release of histamine and PGD2 proceeded in parallel, and the significant correlation between the release of these mediators suggests a common mast cell origin. This hypothesis is supported by cell enrichment experiments using Percoll density gradients. Prostaglandin D2 and histamine release was always associated with those fractions containing mast cells, whereas the generation of TXB2 was mainly associated with cells of the monocyte-macrophage series. The putative 5-lipoxygenase inhibitor 6,9-deepoxy-6, 9-(phenylimino)- 6,8-prostaglandin I1 (U-60,257, Piriprost) had complex inhibitory and potentiating effects on immunoreactive leukotriene C4 generation from ionophore activated human lung cells. The drug also had a surprising potentiating action on PGD2 release, while simultaneously inhibiting the generation of TXB2. The release of prostanoids from human lung cells is discussed in relation to the putative role of prostaglandins in asthma, with particular emphasis on the pharmacological actions of PGD2 on human airway function in vivo.