intracellular distribution. Consequently, LBs fuse in a sequential fashion for up to June Fusion-Activated Ca Although the mechanisms of actin coat contraction have not yet been studied in detail, Ca was stimulated with ATP and phorbol Fura-Measurements of FM Materials and Methods Ethics statement We isolated alveolar type II cells from male Sprague-Dawley rats as described. Rats were obtained from Charles River and maintained at the central animal facility of the Ulm University according to institutional guidelines for ethical care of animals. All experiments in this study were approved by the Regierungsprasidium Tubingen, grant Nr. Cell isolation Rats were anesthetized, and injected with heparin. Lungs were perfused, resected, washed and incubated twice with elastase and trypsin at Darkfield and Fluo-An upright Richardson RTM Experimental conditions Image analysis and data presentation We defined a region of interest encircling the fusing LB in which darkfield light intensity change was measured. 
Fluo-June Fusion-Activated Ca size, whereas the width of the ring was set to approximately Results recording was taken as the start of fluorescence increase. Localized increase in c was detected in N N N different methods to analyze the instance of fusion pore opening. Previous work revealed that the onset of FM The localized post-fusion increase in c was transient, the median half-time of the decrease in Fluo-June Fusion-Activated Ca June Fusion-Activated Ca c increase to Discussion Methodological aspects The major new finding of this study is that exocytotic fusion can trigger Ca N N Could our estimations of the instance of fusion pore formation and rise of c be so imprecise that ��hidden c elevations��prior to fusion are constantly overseen Could the c transients, that we observe, be just random Ca If CaJune Fusion-Activated Ca June Fusion-Activated Ca It is also important to consider in this context that an artifactual misinterpretation caused by possible dye accumulation in LBs, which would measure extracellular Ca Origin of FACE Less clear than the mere fact that fusion triggers c elevations, is the question of its origin: does Ca Pathway and mode of activation of FACE This is largely a matter of speculation. FACE appears to be independent of the mode of cell stimulation: It occurred after submaximal stimulation with ATP, after maximal stimulation with ATP plus phorbol ester and also after stimulation of protein kinase A. Evidence suggesting that an ion channel is involved arises from the time-dependent inhibition by SKF Fusion-Activated Ca the limiting membrane of LB. If Ca N N mechanical chemical Mechanical activation. The strongest argument in favor of a mechanical mode of activation is LB swelling. Many secretory vesicles swell after fusion through osmotic uptake of water by the vesicle matrix, and postfusion LB swelling is considerable, with volume increases up to. June Fusion-Activated Ca locally formed signaling molecules could in 7370771 spread out through the entire cell, the whole spectrum of Ca N N N Actin coat formation and surfactant release Endocytosis Activation of adjacent LBs, possibly for inducing compound exocytosis Actin coat formation and surfactant release. Awareness is growing that postfusion regulation of content release may be relevant to cell physiology in various types of secretion. Beside the known effects
