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 (N BQ) stimulates the in vivo lens regeneration in the adult newt Notopht halmus viridescens and induces a differentiated state in HL-60 leukemi a cells. Because the cytotoxic drug doxorubicin (Adriamycin) induces d ifferentiation of HL-60 cells in vitro we decided to compare the effec t(s) of doxorubicin with NBQ on lens regeneration in vivo. Both drugs were injected intraperitoneally at six different schedules. Morphologi cal criteria of the different regeneration stages were used in the ana lysis of the regenerates. NBQ stimulated lens regeneration independent ly of the time intervals and the stage of regeneration at which the dr ug was administered. There was an increase in the mean number of mitos es suggesting that NBQ stimulated cell proliferation. Doxorubicin admi nistered 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 t erm contact with the tissue. Although NBQ and doxorubicin are both DNA intercalators, they induced the effects on lens regeneration through different mechanisms.