Enhanced 11β-hydroxysteroid dehydrogenase type 1 activity in stress adaptation in the guinea pig

Abstract

The 11β-hydroxysteroid dehydrogenases (11β-HSDs) convert cortisol to its inactive metabolite cortisone and vice versa. 11β-HSD type 1 (11β-HSD-1) functions as a reductase in vivo, regulating intracellular cortisol levels and its access to the glucocorticoid receptor. In contrast, 11β-HSD-2 only mediates oxidation of natural glucocorticoids, and protects the mineralocorticoid receptor from high cortisol concentrations. We investigated the in vivo and in vitro effects of ACTH on the recently characterized 11β-HSDs in guinea pig liver and kidney. Tissue slices of untreated guinea pigs were incubated with 3H-labelled cortisol or cortisone and ACTH1-24 (10-10 and 10-9 mol/l). The 11β-HSD activities in liver and kidney slices were not influenced by in vitro incubation with ACTH1-24. In addition, guinea pigs were treated with ACTH1-24 or saline injections s.c. for 3 days. Liver and kidney tissue slices of these animals were incubated with 3H-labelled cortisol or cortisone. In vivo ACTH treatment significantly increased reductase and decreased oxidase activity in liver and kidney. Furthermore, 11β-HSD-1 activity assessed by measurement of the urinary ratio of (tetrahydrocortisol (THF)+5αTHF)/(tetrahydrocortisone) was significantly increased after ACTH treatment compared with the control group. Plasma levels of cortisol, cortisone, progesterone, 17-hydroxyprogesterone and androstenedione increased significantly following in vivo ACTH treatment. The enhanced reductase activity of the hepatic and renal 11β-HSD-1 is apparently caused by cortisol or other ACTH-dependent steroids rather than by ACTH itself This may be an important fine regulation of the glucocorticoid tonus for stress adaptation in every organ, e.g. enhanced gluconeogenesis in liver.