Metaphase synchronization and chromosome preparation from the OK opossum cell line having a potentially isolatable X chromosome

Growth inhibition and chromosomal instability of cultured marsupial (opossum) cells after treatment with DNA polymerase α inhibitor

The DNA replication mechanism has been well established for eutherian mammals (placental mammals such as humans, mice, and cattle), but not, to date, for metatherian mammals (marsupials such as kangaroos, koalas, and opossums). In this study, we found that dehydroaltenusin, a selective inhibitor of mammalian (eutherian) DNA polymerase α, clearly suppressed the growth of metatherian (opossum and rat kangaroo) cultured cells. In cultured opossum (OK) cells, dehydroaltenusin also suppressed the progression of DNA replication. These results suggest that dehydroaltenusin inhibits metatherian as well as eutherian DNA replication. Dehydroaltenusin treatment of OK cells engendered fluctuations in the numbers of chromosomes in the OK cells as well as inhibition of cell growth and DNA replication. This suggests that partial inhibition of DNA replication by dehydroaltenusin causes chromosomal instability in cultured cells.

Electrical properties of cultured renal tubular cells (OK) grown in confluent monolayers

OK cells grown to confluent monolayers were investigated by microelectrode techniques and microinjection. Cell membrane potential difference (PDm) in bicarbonate-free solution is -61.8 +/- 0.6 mV (n = 208), cell membrane resistance (Rm) amounts to 1.4 +/- 0.2 k omega. cm2 (n = 8). The apparent transference number for potassium (t'k+) is 71 +/- 3% (n = 28) and can be reduced by 3 mmol/l BaCl2 to 7.5 +/- 4.0%; (n = 8). In the presence of extracellular CO2 and HCO3- (pH 7.4) the cells acidify by 0.34 +/- 0.05 pH units (n = 12). This leads to a depolarization of PDm by 8.4 +/- 1.8 mV (n = 8), an increase in Rm by 49 +/- 10% (n = 10), and a reduction of K+-conductance to 63 +/- 5% (n = 13). Intracellular acidification by the NH4Cl-prepulse technique also inhibits K+-conductance and depolarizes the membrane. Recovery from an intracellular acid load is reflected by cell membrane repolarization. This recovery can be inhibited by amiloride (10(-3) mol/l). Na+- and Cl- -conductances could not be detected. The transepithelial resistance (Rte) of OK cell monolayers 1 day after plating is 41 +/- 6 omega.cm2 and decreases with time after plating. Intercellular communication (electrical or dye coupling) was not observed.

CONCLUSIONS

1. The membrane potential of OK cells is largely determined by a pH-sensitive, barium-blockable K+-conductance. 2. Amiloride-blockable Na+/H+-exchange is reflected by membrane potential changes via this K+-conductance. 3. Monolayers of OK cells are electrically leaky.