Glucocorticoid metabolites inhibit the metabolism of androstenedione in red blood cells of ruminants.
The present work aimed to confirm that erythrocytes of ruminants, in general, are capable of converting 17-oxo to 17-hydroxysteroids. Special attention was given to 11-oxoaetiocholanolone (a cortisol metabolite) and its possible interaction with androstenedione as substrates of 17-hydroxysteroid dehydrogenases (17-OH SDH). Blood samples were taken from cattle, sheep and goats (n = 3). Aliquots (100 or 300 microl) of washed red blood cell (RBC) suspensions were incubated in triplicates with Ringer's/glucose solution (1 ml) containing either androstenedione (10 ng) or 11-oxoaetiocholanolone (100 ng) or a mixture of 10 ng of each. Incubations were performed on a shaker at 38 degrees C for 10, 20, 40 or 80 min, respectively. After centrifugation the supernatants were stored at -24 degrees C until analysis. Concentrations of added steroids were measured with enzyme-immunoassays to monitor their decrease. The 17-OH SDH activity of RBC was highest in cattle followed by goats and sheep, and 11-oxoaetiocholanolone was a better substrate than androstenedione. Concentrations of the latter decreased more pronounced, if incubated alone. High performance liquid chromatography separations of the metabolites of 17-oxosteroids revealed the presence of both, a 17beta- and 17alpha-hydroxylated product formed by erythrocytes of sheep and goats, but only the latter in cattle. The results demonstrated that 11-oxoaetiocholanolone was also a substrate of RBC 17-OH SDH and inhibited the metabolism of androstenedione. Therefore, in ruminants, there might be an interaction between cortisol metabolites and gonadal steroids on the level of peripheral steroid metabolism.
El-Bahr
S M
SM
Institute of Biochemistry, University of Veterinary Medicine, Veterinärplatz 1, A-1210 Vienna, Austria.
Möstl
E
E
Palme
R
R
D000735:Androstenedione / Q000493:pharmacokinetics*; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000378:metabolism*; D005043:Etiocholanolone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D005260:Female; D006041:Goats; D008297:Male; D012756:Sheep
D000735:Androstenedione; D005043:Etiocholanolone; C015962:11-ketoetiocholanolone