A comparison of the effects of rapamycin and cyclosporine on kidney and heart morphology in a rabbit heterotopic heart transplant model

Rapamycin (RAPA) or cyclosporine (CsA) was administered intravenously, daily for 60 days, to rabbits with heterotopic heart transplants. Groups of 5 rabbits were randomly assigned to receive RAPA at 0.05,O. 1,0.5 or 1 .O mg/kglday or CsA at either 5 .O, 10.0 or 15 mg/kg/day. Dmg vehicle and saline controls were also included. Animals were examined daily and the cervical allografts assessed by palpation for viabilitylrejection. In those animals in which the heart stopped beating, the heart was removed and processed for light microscopic evaluation. The duration of the study was for 60 days at which time the animals were sacrificed and the transplanted heart and native kidneys removed and processed for light microscopic assessment of rejection and drug toxicity respectively. Biochemical and functional parameters in these animals were previously reported (Transplantation 5: 340-345, 1993). Animals that rejected their grafts were maintained on the dmg until the endpoint of the study to assess toxicity in the native kidneys. The rejected hearts from these animals were also harvested for microscopic evaluation. The results of the study revealed that heart rejection in drug treated animals was significantly lower than in corresponding controls but not different among the various drug treated groups. In the kidney, there were no differences in glomerular tuft area or tuft volume density amongst drug-treated or control animals. In contrast, tubule atrophy and interstitial fibrosis were markedl 3 greater in CsA-treated vs RAPA-treated animals (X 5.00, pe0.02). These data suggest that whereas drug efficacy with respect to heart allograft viability is similar between CsA and RAPA, renal toxicity is significantly less in those animals receiving RAPA

A comparison of cyclosporine A and cyclosporine G in a rabbit heterotopic cardiac transplant model: graft outcome and histological findings

Cervical heterotopic heart transplants were performed on 20 male New Zealand white rabbits comprising 4 treatment groups. Animals in each group were injected daily via the marginal ear vein and received one of the following regimes: Cyclosporine A, 10 mglkglday; Cyclosporine G, 15 mglkglday; cremophor-El, 3mllday; or normal saline. Measurement of 24 hour trough blood concentrations revealed no significant differences between the average concentrations of Cyclosporine A and Cyclosporine G. Animals were examined daily and the cervical allografts assessed by palpation for viabilitylrejection. The duration of the study ended for each animal when the graft stopped beating at which time the animals was euthanized and the transplanted heart and native kidneys harvested and processed for light microscopy evaluation of rejection and drug toxicity, respectively. Graft survival in the Cyclosporine A group significantly surpassed that seen in the Cyclosporine G group as well as the control groups, whereas in animals treated with Cyclosporine G, graft survival was not different from controls. In the native kidney, there were no differences in glomerular tuft area or volume density amongst drug-treated or control animals. In contrast, tubule atrophy and interstitial fibrosis were markedly greater in Cyclosporine A-treated vs Cyclosporine Gtreated animals. The results of this study indicate that, whereas Cyclosporine G is less nephrotoxic than Cyclosporine A, given equivalent blood concentrations Cyclosporine A delays rejection of a cardiac allograft significantly longer than Cyclosporine G in this animal species