RATIOMETRIC IMAGING OF [CA2-LASER SCANNING CONFOCAL MICROSCOPY IN INDO-1-LOADED RAT PANCREATIC ACINUS(](I) DYNAMICS BY UV)

Ratiometric imaging of [Ca2+](i) at a millisecond-order was enabled by confocal UV-laser scanning microscopy in Indo-1-loaded pancreatic aci nar cells. Stimulation with 10 pM CCK-8 induced a [Ca2+](i) rise in th e cellular margin of acinus, which occasionally accompanied an increas e in the luminal area, showing Ca2+ wave propagation from the peripher y to the core of a cell in the confocal plane. The increase in the lum inal region never preceded that in the basolateral region. The [Ca2+]( i) gradient was always from the basolateral to the luminal region. The inward spread of Ca2+ can be interpreted as follows; Ca2+ entry occur s through the entire surface of the basolateral plasma membrane. As ac inar cells are geometrically conical, the luminal region forms three-d imensionally smaller cytoplasmic space, whereas the basolateral region consists of much larger space. This may cause distinct late arrival o f Ca2+ wave at the core of the basolateral region compared with the ea rly arrival at that of the luminal region.