NA-ATPASE EXPRESSION DURING THE EARLY PHASE OF LIVER GROWTH AFTER PARTIAL-HEPATECTOMY(,K+)

Na+,K+-ATPase expression has been studied in the early phase of liver growth after partial hepatectomy to ascertain whether its increased ac tivity is due to stable effects, involving de novo synthesis and inser tion of pumps into the plasma membrane, Na+,K+-ATPase activity progres sively increases after partial hepatectomy, reaching a three-fold indu ction above basal values 12 h after surgery, mRNA amounts of both alph a(1), and beta(1), subunits are rapidly increased up to two-fold for a lpha(1) and nearly three-fold for beta(1), at 9 and 12 h post-hepatect omy, respectively. This correlates with increased abundance of both su bunit proteins. The results prove that the increase of Na+,K+-ATPase a ctivity correlates with higher expression of both subunit proteins and mRNAs, although the characteristics of the induction suggest that som e translational and post-translational events may be equally involved in the increased activity of the pump.