Angiostatic activity and metabolism of cortisol in the chorioallantoic membrane (CAM) of the chick embryo

Loretta G. McNatt, Deborah Lane, Abbot Clark

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There is considerable interest in the discovery of compounds which inhibit angiogenesis dependent (neovascular) diseases. The chick embryo, due to the rapid development of an extensive vascular capillary network in the chorioallantoic membrane (CAM), has been used extensively as a model for studying angiogenesis. Angiostatic steroids are a new class of compounds which inhibit the growth of new capillaries in the chick CAM and in other models of neovascularization. Despite the potential therapeutic importance of these compounds, little is known about the ability of the CAM to metabolize these steroids. We have evaluated the ability of the chick CAM to metabolize cortisol which is both an angiostatic steroid as well as a glucocorticoid. When CAM homogenate was incubated with [3H]cortisol and NADPH at 37°C and pH 7.4, and the reaction products analyzed by reverse phase HPLC, [3H]cortisol was converted exclusively to 20β-dihydrocortisol (4-pregnen-11β,17α,20β,21-tetrol-3-one). The cortisol metabolite, 20β-dihydrocortisol, has very little glucocorticoid activity, but shows significant angiostatic activity in the CAM comparable to cortisol. The apparent Km determined for cortisol metabolism was 12 μM and the observed Vmax was 1.4 μmol cortisol/mg protein/min. The majority of the 20β-reductase activity was found in the soluble (242,000 g) fraction of CAM homogenate. 20β-Reductase activity in chick embryo CAM has not been previously reported.

Original languageEnglish
Pages (from-to)687-693
Number of pages7
JournalJournal of Steroid Biochemistry and Molecular Biology
Issue number7
StatePublished - 1 Jan 1992


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