Cardiac troponin I in isoproterenol-induced cardiac injury in the Hanover Wistar rat: studies on low dose levels and routes of administration.

The current studies demonstrate the effect of low-dose intraperitoneal (IP) administration of isoprotenerol (ISO) and subcutaneous (SC) versus IP routes of administration of ISO on serum cardiac troponin I (cTnI) levels in female Hanover Wistar rats, providing additional evidence to support acceptance of cTnI as a cardiac biomarker. At 2 hr postdosing with 0-500 microg/kg ISO, mean serum cTnI levels were increased in a dose-related fashion at > or =10 microg/kg with no evidence of cardiac pathology. At 24 h, cTnI concentrations were generally at control levels, but histologic cardiomyocyte injury was evident in a proportion of the animals given > or =10 microg/kg. In a second experiment, rats given SC ISO at 5,000 microg/kg and necropsied at 0, 1, 2, and 4 hr postdosing had higher levels of serum cTnI than animals given the same dose IP.