Lanthanum‐Induced alterations in cellular electrolytes and membrane potential in ehrlich ascites tumor cells

Publisher Website
Google Scholar
Abstract
We have investigated the effect of varying La+3 concentrations (0.01 mM to 2.0 mM) on membrane potential and electrolyte composition of Ehrlich ascites tumor cells. La+3 concentrations less than 0.02 mM had no effect. Above 0.02 mM, La+3 induced concentration‐dependent loss of electrolytes and water from the cells. At 1.0 mM the effect was maximal and resulted in an 87% reduction in cellular K+, 79% in Cl− and 21% in Na+ within 4.8 minutes. The Na+ loss occurred even in the face of an electrochemical potential gradient favoring Na+ entry. La+3 increased the recorded values of membrane potential; the magnitude of the effect was related to the external La+3 concentration, and was maximal at 1.0 mM. Studies using 140La showed that La+3 binds rapidly to the cell surface and does not enter the cells. The amount of La+3 bound to the cells was related to the external La+3 concentration by a sigmoidal curve and was maximal at about 1.0 mM. The bound La+3 could not be displaced by either added La+3 or Ca+2. Agents known to effect the integrity of the cell membrane, such as phospholipase C, neuraminidase, pronase and Hg+2 were tested for their ability to displace bound La+3. Only pronase displaced bound La+3, indicating that La+3 associates with cell protein. It is hypothesized that La+3 rapidly interacts with membrane protein causing alterations in membrane permeability and capacity to actively transport ions.