Pharmacological preconditioning of primary rat cardiac myocytes by FK506.

Pre-treatment with the immunosuppressant FK506 is shown to protect primary cardiocytes against a subsequent severe thermal or ischaemic stress. This effect is not observed with the related compounds cyclosporin A or rapamycin. It does not involve induction of the FK506 binding, heat inducible protein hsp56 or of the other heat shock proteins. In addition over-expression of hsp56 does not protect cardiac cells from severe stress in contrast to our previous results with hsp70 and hsp90. These results suggest the FK506 is acting via a novel mechanism to protect cardiac cells against cellular ischaemia which may not be related to its immunosuppressant action.