PRIMARY CULTURE OF RABBIT PROXIMAL TUBULES AS A CELLULAR-MODEL TO STUDY NEPHROTOXICITY OF XENOBIOTICS

The effects of gentamicin treatment on functions of the plasma membran e-bound proteins in situ were investigated in primary culture of rabbi t proximal tubular cells (PTC), a recognized model of renal epithelial cells. Activities of apical and basolateral enzymes, activities of ph osphate, glucose and alanine sodium-coupled transport systems and leak age of the cytosolic enzyme lactate dehydrogenase (LDH) were determine d in PTC grown in glucose-free culture medium as confluent monolayers and incubated with the aminoglycoside. Gentamicin altered in a concent ration- and time-dependent manner the activity of dipeptidyl peptidase IV (DPP IV), neutral aminopeptidase (NAP), Na+K+-ATPase and the V(max ) of sodium-dependent glucose and phosphate uptake, whereas gamma-glut amyl-transpeptidase (GGT) and sodium-dependent alanine uptake were una ffected. Identical concentration of gentamicin was required to induce LDH leakage and cell functions impairment. In contrast, under short ti me exposure, a condition where the enzyme activities were untouched, m ercuric chloride inhibited to a similar extent the activity of the thr ee sodium-coupled transport systems. These data suggest that whereas a lterations in membrane fluidity might mediate the effects of gentamici n on membrane functions, the inhibition of transports by mercuric chlo ride rather reflects an effect on sodium permeability of the apical me mbrane. They also suggest that study of Na+-coupled transports in prox imal tubular cells grown in primary culture is a simple and sensitive in vitro model to assess drug-induced nephrotoxicity.