Different sensitivity to nephrotoxic agents and osmotic stress in proximal tubular and collecting duct cell lines derived from transgenic mice

Abstract

We established six renal tubular cell lines from definite tubular areas of the kidney of transgenic mice harboring tsSV40 large T-antigen gene. Three are proximal tubular cell lines prepared from the S1, S2 and S3 segments of the proximal tubule and the others are collecting duct cell lines obtained from cortical, outer medullary and inner medullary collecting ducts (CCD, OMCD and IMCD, respectively). To verify the growth properties of these cell lines under different temperature conditions (33 and 39 °C), two representative cells were chosen from the proximal tubule (S1 cells) and from the collecting duct (IMCD cells). From these cells, a daily change in cell number was evaluated as a parameter of cell growth. As might be expected, cell numbers of these cells increased only at 33 °C. Similar patterns were also observed with the other cell lines. To observe the different sensitivity to nephrotoxic agents in proximal tubular cell lines, the cells were exposed to nephrotoxic agent, gentamicin, ochratoxin A or cisplatin. Gentamicin (1 mg/ml) dose-dependently decreased cellular ATP levels of the S1 cells only. In contrast, the effect of ochratoxin A (10−6m) was most pronounced in the S2 cells, and that of cisplatin (10 μg/ml) in the S3 cells. To characterize collecting duct cell lines, a hyperosmotic challenge of 700 or 1100 mOsm/l was applied to the cells. At an isoosmotic condition of 300 mOsm/l, the number of cells from the collecting ducts, regardless of their origin, increased continuously during the culture period of 4 days. At an osmotic concentration of 700 mOsm/l, the number of CCD cells decreased, while OMCD cells showed a gradual but a significant increase in cell numbers throughout the culture period. IMCD cells, however, proliferated even at a concentration as high as 1100 mOsm/l, although an initial decrease in cell number was noted on the first day of culture. For confirmation of intracellular free calcium ([Ca2+]i) mobilization, cells were treated with ATP and bradykinin. The [Ca2+]i was increased significantly and immediately by ATP (10−4m) in S1 cells and bradykinin (10−7m) in IMCD cells. From the results obtained, it is indicated that renal tubular cell lines from transgenic mice have different sensitivities to nephrotoxic or osmotic stress showing the conservation of the functional characters of the definite part it originated from.