Effects of 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQ) and doxorubicin on lens regeneration in the adult newt: a morphological study.

The antitumor drug 3-nitrobenzothiazolo [3,2-a] quinolinium chloride (NBQ) stimulates the in vivo lens regeneration in the adult newt Notophthalmus viridescens and induces a differentiated state in HL-60 leukemia cells. Because the cytotoxic drug doxorubicin (Adriamycin) induces differentiation of HL-60 cells in vitro we decided to compare the effect(s) of doxorubicin with NBQ on lens regeneration in vivo. Both drugs were injected intraperitoneally at six different schedules. Morphological criteria of the different regeneration stages were used in the analysis of the regenerates. NBQ stimulated lens regeneration independently of the time intervals and the stage of regeneration at which the drug was administered. There was an increase in the mean number of mitoses suggesting that NBQ stimulated cell proliferation. Doxorubicin administered for five days did not modify the regenerative process. On the other hand, doxorubicin given for periods of nine or more days after lentectomy, strongly inhibited the formation of a new lens. Thus, the inhibitory effect of doxorubicin is dependent on the continuous long term contact with the tissue. Although NBQ and doxorubicin are both DNA intercalators, they induced the effects on lens regeneration through different mechanisms.