Insulin modulation of pyruvate dehydrogenase in human circulating lymphocytes.

1. In human circulating lymphocytes pyruvate dehydrogenase (PDH) complex is present in the active (PDHa) and inactive (PDHi) forms. 2. PDHi conversion into PDHa is stimulated when intact lymphocytes are incubated with 5 microU/ml insulin at pH 7.4, for 15 min at 37 degrees C in a medium supplemented with 50 microM Ca2+-Mg2+. 3. The generation of a mediator is strongly suggestive since a cell free preparation from circulating lymphocytes, treated as above described, still stimulates PDHi----PDHa conversion, when combined with either disrupted or intact lymphocytes.