THE RÔLE OF POTASSIUM IN MYASTHENIA GRAVIS.

Abstract

(RECEIVED 28THNOVEMBER, 1939) IThasbeenshownthat theaffected muscles ofpatients suffering frommyasthenia gravis contain morepotassium thannormalmuscles (Cumings, 1939b), and that after thesubcutaneous administration vfprostigmin tomyasthenic patients, theconcentration ofpotassium intheir muscles fell toanormal level, andalso inoneofthecases recorded inthatpapertheserumpotassium wasobserved to rise asthemuscle potassium fell. Thepresent paperdeals withastudy ofthe fate ofthepotassium leaving themuscles. Twopatients withsevere myasthenia affecting themuscles oftheextremities aswellasthose oftheneckwerechosen, andfortheperiod oftheexperiment weregiven adiet containing aknownamountofpotassium. Themealswere prepared fromweighed quantities ofmilk, sugar, apple, tomato, bread, butter, chicken, fish, egg,potato, cheese, andrice, andtheamountofpotassium was determined ineachofthese foods.Distilled waterwasusedforallpurposes. Although oneofthetwopatients received arather moreliberal diet andone whichatthesametimecontained alarger amountofpotassium, neither patient received quite asmuchpotassium intheir foodasanormal person wouldhave done. Theurine wascollected inthree 4-hourly periods during theday, andone 12-hour period during thenight (e.g. from8a.m.to12noon,12to4p.m., 4to8p.m., and8p.m.to8a.m.). Thestools werecollected separately, charcoal being usedtodemarcate theperiods. Thevolumes ofeachurine specimen, andtheweights ofthedried stools wererecorded. Neither patient received prostigmin oranyother therapy forthefirst two experimental days, butonthethird eachwasgiven prostigmin (mgm.1)subcutaneously attheendofoneofthe4-hourly periods (at4p.m.). Eachday fromthefourth daytotheendoftheexperimental period bothpatients were given 3gms.ofpotassium intheformofdipotassium hydrogen phosphate. Themeasure waswashed outwithdistilled waterafter eachdoseandthewashings administered tothepatients.