Expression and function of sodium transporters in two opossum kidney cell clonal sublines

The present study describes characteristic features of two clonal subpopulations of opossum kidney (OK) cells (OKLC and OKHC) that are functionally different but morphologically identical. The most impressive differences between OKHC and OKLC cells are the overexpression of Na+-K+-ATPase and type 3 Na+/H+ exchanger by the former, accompanied by an increased Na+-K+-ATPase activity (57.6+/-5.6 vs. 30.0+/-0.1 nmol P-i.mg protein(-1).min(-1)); the increased ability to translocate Na+ from the apical to the basolateral surface; and the increased Na+-dependent pH(i) recovery (0.254+/-0.016 vs. 0.094+/-0.011 pH units/s). V-max values (in pH units/s) for Na+-dependent pH(i) recovery in OKHC cells (0.00521+/-0.0004) were twice (P<0.05) those in OKLC (0.00202 +/- 0.0001), with similar K-m values (in mM) for Na+ (OKLC, 21.0 +/- 5.5; OKHC, 14.0 +/- 5.6). In addition, we measured the activities of transporters (organic ions, alpha-methyl-D-glucoside, L-type amino acids, and Na+) and enzymes (adenylyl cyclase, aromatic L-amino acid decarboxylase, and catechol-O-methyltransferase). The cells were also characterized morphologically by optical and scanning electron microscopy and karyotyped. It is suggested that OKLC and OKHC cells constitute an interesting cell model for the study of renal epithelial physiology and pathophysiology, namely, hypertension.