Objective To observe the expression of perforin and granzyme B mRNA in peripheral blood lymphocytes dynamically after heart transplantation in rats,and to assess the relationship between their expression level and acute cardiac allograft rejection.Methods The donor's heart and up-right lung were transplanted into the recipient's abdomen by the donor ascending aorta anastomized with recipient abdominal artery.The rats were divided into two groups after operation,the experimental group(n = 17),the donors were Wistar and the recipients were SD rats.The control group(n = 18),the transplantation was performed just between SD rats.FQ-PCR was used to quantify the perforin and granzyme B mRNA level in peripheral blood lymphocytes at varying times,meanwhile the graft was harvested to examine the pathological changes.Results At 24 hours after transplantation,the expression of perforin and granzyme B mRNA began to be up-regulated,reaching the peak at 3 to 5 days,and still kept a high level at 7-11 days.There was a significant difference in comparison with the level before operation and the expression level of control group(P<0.001).Those changes occurred earlier than the pathological changes.No changes were observed in the control group.Conclusion The graft rejection is concomitant with the expression of perforin and granzyme B mRNA.The expression level of perforin and granzyme B mRNA is changed earlier than pathological changes.The measurement of perforin and granzyme B mRNA may be a good indicator of acute rejection.