FORMATION OF ACTIN FILAMENT NETWORKS IN CULTURED RAT HEPATOCYTES TREATED WITH DMSO AND GLUCAGON

Actin filament organization may play an important role in the maintena nce of differentiated functions in epithelial cells, We previously rep orted our success in inducing and maintaining gap junctions, which are two kinds of differentiated function, in primary rat hepatocytes cult ured with 2% DMSO and 10(-7) M glucagon, In the present study, we demo nstrated the formation of actin filament networks in the hepatocytes c ultured with 2% DMSO and 10(-7) M glucagon, Actin filaments in hepatoc ytes cultured in medium with only 2% DMSO added from 96 h after platin g were concentrated under the plasma membrane and were observed to be circumferential. In hepatocytes cultured in the medium with both 2% DM SO and 10(-7) M glucagon added from 96 h, not only the circumferential actin filaments but also the formation of actin filament networks wer e observed and the networks developed well with time in culture. The n etworks were observed as a dome-like structure under the cell face and terminated at the circumferential actin filaments, They were composed of electron-dense star-like vertices connected by microfilament bundl es of varying length and were also very sensitive to the actin disrupt er cytochalasin B, However, during the network formation, there were n o significant increases in the amounts of actin protein and mRNA, The actin filament networks of the hepatocytes in this culture system migh t be closely related to the maintenance of differentiated functions.