HIGH-PURITY RYANODINE AND 9,21-DEHYDRORYANODINE FOR IN-VITRO DIAGNOSIS OF MALIGNANT HYPERTHERMIA IN MAN

Susceptibility to malignant hyperthermia (MH) is currently diagnosed b y the in vitro contracture test (IVCT) in skeletal muscle. However, th is test does not possess absolute specificity. Thus, in addition to th e established procedure, the ''ryanodine contracture test'' has been p roposed to improve discrimination between MH-susceptible (MHS) and nor mal (MHN) patients. in all previous studies, the ryanodine used was a mixture consisting of high-purity ryanodine (HPR) and 9,21-dehydroryan odine (DHR). Therefore, in this study the effects of both substances w ere investigated in concentrations of 2, 5 and 10 mu mol litre(-1). Wi th all concentrations, contractures appeared earlier in MHS than in MH N muscles, but these differences were significant at all contracture l evels with HPR only. Moreover, with the smallest concentration (2 mu m ol litre(-1)), the best discrimination between MHS and MHN was observe d. Classification of MH-equivocal patients (MHE) as MHS or MHN seems 5 0 be possible with the use of ryanodine-induced contractures. The cont racture test with HPR should therefore be added to the established pro cedure of the IVCT.