Oral immunosuppressive medication for growing pigs in transplantation studies

Immunosuppressive (IS) medication is needed to avoid graft rejection in porcine transplantation models. An ideal IS therapy should have no side-effects, but increased susceptibility to infections, disturbed intestinal microflora and toxic effects on organs and tissues are commonly reported. The aim of the present study was to design an IS protocol with tacrolimus and mycophenolic acid to be used for maintenance therapy in the post-transplant period. An eligible whole blood trough value for tacrolimus was 5-15 μg/L. Conventional specific pathogen-free pigs were fitted with an indwelling catheter under general anaesthesia, and after the acclimatization period three groups were formed: group A (n= 4) received 0.15 mg/kg body weight (BW) twice daily tacrolimus and 500 mg twice daily mycophenolic acid; group B (n= 4) received 0.3 mg/kg BW twice daily tacrolimus and 500 mg twice daily mycophenolic acid; group C (n= 2) did not receive any medication. Daily clinical examinations and analyses of blood concentrations of tacrolimus and glucose were performed. Total and differential white blood cell counts, enzyme activities, bilirubin and electrolyte concentrations were measured every fourth day. At the end of the experiment, the pigs were killed with an overdose of pentobarbital intravenously and a necropsy was performed immediately. All animals seemed to tolerate the IS treatment well. No alterations in their clinical state of health were observed throughout the study and daily weight gain was similar for the three groups. The necropsy did not reveal any pathological findings related to medication. The study showed that 0.25 mg/kg BW twice daily tacrolimus and 500 mg twice daily mycophenolic acid would be an appropriate maintenance dosage for conventional pigs.