Technetium-99m pyrophosphate in diagnosis of acute cardiac rejection in the rat with effect of cyclosporine: concise communication.

Tc-99m pyrophosphate (PPi) uptake has been measured in a rat model of heterotopic heart transplant at 5 days after transplantation. comparison of tracer uptake, as a ratio between the heterotopic transplanted heart and the recipient's native heart, was made in four groups of animals. Group 1, with transplants between animals of isogeneic strain showed a lower ratio, significantly different from the ratio in Group 2 in which transplants were between nonisogeneic animals. The ratio of uptake after transplantation between nonisogeneic animals treated with 10 mg/kg-day of cyclosporine (Group 3), was not significantly different from Group 1. In contrast, the ratio of uptake between nonisogeneic animals treated with subtherapeutic doses of cyclosporine (Group 4), was not significantly different from Group 2. In Groups 1, 2, and 3 there was a correlation between the histology of the transplanted hearts, graded 1 to 5 according to the severity of rejection, compared with the uptake of Tc-99m PPi. This agent can therefore be used to diagnose cardiac rejection in a rat model, and the results correlate well with the severity of rejection as assessed histologically.