Ursodeoxycholate promotes protein phosphorylation in the cytosol of rat hepatocytes

A study is presented of the effect of the bile salt ursodeoxycholate (UDC) on protein phosphorylation by [gamma-32P]ATP in the cytosol from rat hepatocytes. Gel electrophoresis and corresponding autoradiograms of cytosolic proteins show that UDC promotes phosphorylation of at least eight different protein bands. Four of them (the 36, 60, 64 and 76 kDa) are phosphorylated by Ca2+ and phospholipid-dependent protein kinase (PKC); three (the 31, 51 and 71 kDa) are phosphorylated by cAMP-dependent protein kinase (PKA) and one protein band, with molecular weight of 34 kDa, apparently contains substrates of both PKC and PKA. Data are reported indicating that UDC can directly affect the intrinsic activity of protein kinases.