HEPATOCYTE GROWTH FACTOR-INDUCED CALCIUM WAVES IN HEPATOCYTES AS REVEALED WITH RAPID-SCANNING CONFOCAL MICROSCOPY

Cytosolic Ca2+ transients induced by hepatocyte growth factor (HGF) were imaged in primary cultured rat hepatocytes using newly developed rapid scanning confocal microscopes and Indo-1. HGF (40 ng/ml) increased cytosolic free Ca2+ concentration ([Ca2+](i)) In about 60% of hepatocytes, in 45% of which the increases were oscillatory. In each of the oscillatory hepatocytes, the repetitive increases in [Ca2+](i) originated from a specific same region adjacent to the cell membrane and propagated across the cell like waves. Phenylephrine (10 mu M) also induced Ca2+ waves. The locus where HGF-induced Ca2+ waves and phenylephrine-induced Ca2+ waves were originated was the same, and there was a correlation in the peak height between HGF-induced Ca2+ waves and phenylephrine-induced Ca2+ waves in each cell, although the mechanisms of inositol 1,4,5-trisphosphate (Ins(1,4,5)P-3) formation induced by HGF should be different from those by phenylephrine. On the other hand, there was no correlation between sensitivity of each cell to HGF and that to phenylephrine which were measured as latent periods prior to Ca2+ rises after an addition of the agonists. These results suggested the following: the spatial patterns of Ca2+ waves were decided by a common mechanism, probably not the propagation of Ins(1,4,5)P-3 but the distribution of Ins(1,4,5)P-3-sensitive Ca2+ pools; sensitivities of each cell to the agonists did not mainly depend on the common mechanism.