Synthetic adrenocorticotropin for optimizing murine circadian chronotolerance for adriamycin.
An attempt to pre-set the circadian rhythm in murine chronotolerance for adriamycin (ADR) given i.p. or i.v. with ACTH was performed in three studies. In CDF1 mice standardized in LD12:12, it was demonstrated that 1) the circadian rhythm in murine chronotolerance for ADR exhibits a different timing depending upon whether the intravenous or intraperitoneal route is used for the administration of this anticancer agent; 2) ACTH or saline pretreatment does not enhance optimal circadian-stage-qualified ADR tolerance, whatever its route of injection, with any of the circadian stages and schedules explored; 3) near-optimal tolerance can be achieved by a fixed 'best' interval (among those investigated) between ACTH and ADR, irrespective of circadian stage. Tolerance equivalent to optimal circadian-stage-qualified ADR tolerance results from the administration of ACTH 1-17 (HOE433 = Synchrodyn) 24 hours before ADR injection; 4) and acrophase advance of over 6 hours of the tolerance rhythm results from ACTH 1-17 administration at 6 HALO. The acrophase changes do not directly account for an optimal ADR tolerance at a fixed interval of 24 hours after ACTH 1-17. Thus, ACTH may be considered a potential relative chronizer of murine chronotolerance for ADR.