Fig. 6.

Schematic describing how cardiotonic induced sodium pump signaling may result in decreases in collagen production. In the presence of the cardiotonic steroid MBG, Na-K-ATPase is converted to a signal transducer that complexes with Src and the EGF receptor (EGFR). A signal cascade is initiated that involves PLC, which results in the activation of PKCδ and its translocation to the nucleus. In the nucleus, PKCδ phosphorylates Fli-1. This, in turn, leads to more rapid catabolism of Fli-1 and removal of Fli-1 inhibition on the Col1 promoter and thus increases in collagen expression.