Sphingomyelinase activities of various human tissues in control subjects and in Niemann-Pick disease - development and evaluation of a microprocedure.

A micromethod was elaborated for the assay of sphingomyelinase activities with native labelled substrate in leukocytes, cultivated skin fibroblasts, liver tissue and cultivated amniotic fluid cells. The optimal assay conditions and specific activities in control samples were investigated for each enzyme souce. No significant difference was found between results obtained either with the micromethod or with our previous procedure. Findings obtained in pathological material from 62 patients with the various forms of Niemann-Pick disease and 21 obligate heterozygotes by one or another method are reported. A generalized severe sphingomyelinase deficiency was observed in all cases with Niemann-Pick disease type A or B, while in Niemann-Pick disease type C, sphingomyelinase activities were normal in leukocytes, elevated in liver tissue and partially deficient in cultivated skin fibroblasts. Six pregnancies at risk were monitored.