Platelet activating factor (PAF) stimulates the secretion of surfactant by rat type II cells with the same increment and time course as tetradecanol phorbol acetate (TPA)

TPA induces a 5 to 6 fold increase in surfactant secretion by Type II cells in primary culture. To date however, a natural secretatogue for surfactant using the pathway activated by TPA has not been described. Since TPA may exert its effects on Type II cells through protein kinase C, which, in platelets, may also be activated by PAF, the authors reasoned that PAF might influence the metabolic activities of Type II cells. Rat alveolar Type II cells in primary culture for 24 hours were washed and presented with 32P/sub i/ and either 10-9M PAF, 10-6M TPA or solvent. Incorporation of 32P/sub i/ into total PC of cells and media was quantified at 2, 4, and 6 hours. The authors found that the secretion of total PC was stimulated over control by 5 to 6 fold by both PAF and TPA, and the effects exerted by the two substances followed similar time courses. The authors had previously found that these cell cultures incorporated 3H-lyso-glycerylether phosphocholine into PAF, and they contained 0.2- 1 pmol PAF per 106 cells. These results present the possibility that Type II cells may synthesize PAF and use it in the regulation of surfactant metabolism, perhaps through a pathway similar to that exerted by TPA