Synthesis of corticosterone in the vascular wall.

Extra-adrenal steroid 21-hydroxylation and 11 beta-hydroxylation occur in a variety of human tissues. This study was undertaken to determine whether the rat mesenteric artery produces corticosterone and to demonstrate the CYP11B1 mRNA in the vascular tissue. Isolated rat mesenteric arteries were perfused with Krebs-Ringer solution for 4 h. The perfusate was collected and chromatographed in a reverse-phase HPLC system. The fraction corresponding to synthetic corticosterone was collected and analyzed by mass spectrometry. The concentration of corticosterone in the perfusate from the adrenalectomized rats was measured using radioimmunoassay after separation with the HPLC system. The mass spectra of synthetic corticosterone was identical with corticosterone isolated from the perfusate of the rat mesenteric arteries. The radioactive peak of corticosterone was detected in the perfusate after perfusing the mesenteric artery with Krebs-Ringer solution containing [14C]-pregnenolone. The expression of CYP11B1, 11B2, and 11A mRNA was detected in the mesenteric artery using a RT-PCR. The production of corticosterone in the vascular wall was increased in the adrenalectomized rats compared with that of the controls. This study shows that the rat mesenteric artery produces corticosterone, and the corticosterone synthase is existed in the vasculature.