In vivo distribution of some 17-hydroxycorticosteroids between the plasma and red blood cells of man

Various corticosteroids (cortisol, tetrahydrocortisol or tetrahydrocortisone intravenously, 1 mg. per Kg. of body weight; 4-C¹⁴-cortisol intravenously, 1 microcurie; cortisol or cortisone acetate orally, 100 mg.) were administered to normal adult subjects. Blood samples were obtained at specific intervals following administration of steroid. 17-Hydroxycorticosteroid (17-OH-CS) extracts of red cells and plasma were prepared. In all cases, a significant fraction of the free 17-OH-CS of the various blood samples was associated with the red cells (average, 25.1 per cent; range, 17.7 to 36.5 per cent), whereas the total amount of the 17-OH-CS glucuronides was found in the plasma.