Journal Article

Involvement of ERK1/2 and p38 in Mg super(2+) accumulation in liver cells

Perry, Beverly, Cefaratti, Christie, Torres, Lisa M, Romani, Andrea

2006

Overview

Activation of PKC signaling induces Mg super(2+) accumulation in liver cells. To test the hypothesis that PKC induces Mg super(2+) accumulation via MAPKs activation, hepatocytes were incubated in the presence of PD98059 and SB202190 as specific inhibitors of ERK1/2 and p38, respectively, and stimulated for Mg super(2+) accumulation by addition of PMA or OAG. Accumulation of Mg super(2+) within the cells was measured by atomic absorbance spectrophotometry in the acid extract of cell pellet. The presence of either inhibitor completely abolished Mg super(2+) accumulation irrespective of the dose of agonist utilized while having no discernible effect on b -adrenoceptor mediated Mg super(2+) extrusion. A partial inhibition on a sub(1)-adrenoceptor mediated Mg super(2+) extrusion was observed only in cells treated with PD98059. To confirm the inhibitory effect of PD98509 and SB202190, total and basolateral liver plasma membrane vesicles were purified in the presence of either MAPK inhibitor during the isolation procedure. Consistent with the data obtained in intact cells, liver plasma membrane vesicles purified in the presence of PD98509 or SB202190 lost the ability to accumulate Mg super(2+)in exchange for intra-vesicular entrapped Na super(+) while retaining the ability to extrude entrapped Mg super(2+) in exchange for extra-vesicular Na super(+). These data indicate that ERK1/2 and p38 are involved in mediating Mg super(2+) accumulation in liver cells following activation of PKC signaling. The absence of a detectable effect of either inhibitor on b -adrenoceptor induced, Na super(+)-dependent Mg super(2+) extrusion in intact cells and in purified plasma membrane vesicles further support the hypothesis that Mg super(2+) extrusion and accumulation occur through distinct and differently regulated transport mechanisms.

• Subject: Absorbance