Involvement of calcium in the stimulation of phosphatidylcholine secretionin primary cultures of rat type II pneumocytes by Escherichia coli lipopolysaccharide

The purpose of this study was to evaluate the mechanism by which Escherichi a coli lipopolysaccharide stimulates the secretion of phosphatidylcholine i n primary cultures of rat type II pneumocytes. The stimulatory effect of li popolysaccharide on phosphatidylcholine secretion was additive to those of terbutaline and TPA (protein kinase A and C activators respectively) and th is effect was not suppressed by inhibitors of both protein kinases. On the other hand, lipopolysaccharide did not modify the increase on phosphatidylc holine secretion induced by the endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin, and enhanced slightly the calcium-ionophore A23187 stimulate d phosphatidylcholine secretion. In addition, the stimulatory effect of lip opolysaccharide was suppressed by BAPTA, an intracellular Ca2+ chelator, an d KN-62, a specific inhibitor of Ca2+-calmodulin-dependent protein kinase. These results, together with the lipopolysaccharide-mediated increase in th e cytosolic [Ca2+], suggest that stimulation of phosphatidylcholine secreti on by lipopolysaccharide in type II pneumocytes occurs by a calcium-depende nt transduction mechanism via Ca2+-calmodulin-dependent protein kinase acti vation.