The effect of lucanthone on sublethal radiation damage, in vivo

The capacity of the Chinese hamster jejunal crypt cell to accumulate and repair sublethal radiation damage was determined by analyzing the return of the shoulder of the radiation dose-crypt microcolony survival curve (Dr) after a priming dose of 1250 rad. The control split dose crypt cell survival curve exhibited a D0, Dr and "n" of 179 +/- 3 rad, 261 +/- 3 rad and 4.3 respectively; repair of sublethal radiation damage was completed by two hours post-irradiation. The effect of lucanthone (an antischistosomal DNA intercalating agent) on the crypt cell's capacity to accumulate and repair sublethal radiation damage was determined by injecting the drug (100 mg/kg, i.p.) at intervals before irradiation with a priming dose of 1250 rad, followed two hours later by graded doses. Injection coincident with the priming dose of radiation resulted in a 22 rad reduction of the Dr (compared to control Dr). Injection eight hours before the priming dose almost completely inhibited the accumulation and repair of sublethal radiation damage so that the resultant Dr two hours later was only 29 rad (a 232 rad reduction). At no time was the D0 of the crypt cell survival curve affected by lucanthone. These data confirm previous results from whole crypt analysis and LD50/7 analysis that non-toxic concentrations of lucanthone reversibly inhibit the accumulation and repair of sublethal radiation damage in a time-dependent manner with complete inhibition approximately eight hours post-injection. This drug is useful for the study of sublethal radiation damage in vivo and may be beneficial in radiation therapy of cancer when it is desirable to inhibit the repair of sublethal radiation damage.