The in vivo metabolism of progestins. IV. The metabolic clearance rate and plasma binding of 6alpha-methylpregn-4-ene-3, 20-dione in women.
[3H]6alpha-methylprogesterone (6MP) was synthesized by selective catalytic tritiation of the delta1-olefinic bond of 6alpha-methylpregna-1,4-diene-3,20-dione. The metabolic clearance rate of 6MP (MCR6MP) was determined in 6 women by the single injection technique. The plasma MCR6MP was 4047 +/- 298 L/day (59 +/- 15 L/day/kg) which was higher than the MCR of progesterone and medroxyprogesterone acetate (6alpha-methyl-17alpha-hydroxy-pregna-4-ene-3,20-dione acetate). The high clearance was not due to binding or metabolism of 6MP by red cells. Although 6MP was bound to CBG with a lower affinity than progesterone, this could not entirely explain the high MCR6MP. When considered with the reports of progesterone and medroxyprogesterone acetate clearance, the present studies suggest that the 6alpha-substitution of progesterone leads to an increased rate of steroid metabolism in women.
D002352:Carrier Proteins / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006801:Humans; D008525:Medroxyprogesterone / Q000031:analogs & derivatives / Q000097:blood; D008657:Metabolic Clearance Rate; D011282:Pregnenediones / Q000097:blood*; D011374:Progesterone / Q000097:blood
D002352:Carrier Proteins; D011282:Pregnenediones; D011374:Progesterone; D008525:Medroxyprogesterone