Phosphorescence of 8-azasteroids and related compounds.
We have investigated the electron absorption, fluorescence and phosphorescence spectra of 8-azasteroids and model compounds containing enaminodicarbonyl fragment. It has been shown that the investigated compounds have absorption and phosphorescence spectra similar in form and position. The results obtained permit the conclusion that the main deactivation channel of the excited singlet state is the intersystem crossing. It is suggested that the investigated 8-azasteroids of enaminodicarbonyl series under light irradiation undergo phototransformations presumably into derivatives with a gamma-pyridone fragment.
Fluorescence detection of cardenolides in reversed-phase high-performance liquid chromatography after post-column derivatization.
Methods for the fluorescence derivatization of cardiac glycosides with concentrated acids from TLC are adopted to HPLC for post-column derivatization. The column effluent is blended with concentrated acids in a knitted tube reactor, which enables derivatization with negligible increase in chromatographic peak width. The selectivity of the reaction is temperature-dependent and influenced by the respective acid. Reactivity increases from H3PO4-->CH3SO3H[symbol: see text]H2SO4. The conversion of digoxigenin, digitoxigenin and their digitoxosides is accelerated by Cu(II) acetate or Co(II) nitrate in H2SO4. Combined with a new two-mode, single-column solid-phase sample preparation, cardiac glycoside levels of less than 100 pg/glycoside in 1 ml plasma are detectable.
Ouabain is secreted by bovine adrenocortical cells.
Ouabain is a specific inhibitor of the sodium pump. This steroid has been found in the mammalian circulation in significant amounts and may be of adrenal origin. Secretion of ouabain from adrenal cells has been little studied and the purpose of the present work was to determine the adrenal distribution of ouabain, aldosterone and cortisol, and to characterize the effects of ACTH and angiotensin II on the secretion of these steroids in primary cultures of bovine adrenocortical cells. In fresh bovine adrenals, the cortical to medullary ratios for aldosterone, cortisol and ouabain were 14, 4.25 and 2.5, respectively. All three steroids were detected in elevated amounts in the conditioned medium of primary cultures of adrenocortical cells. Reverse phase HPLC of the secreted ouabain immunoreactivity showed it was isopolar with commercial ouabain. In the presence of 10 nM ACTH or angiotensin II, the secretion of all three steroids increased significantly with similar time courses. The stimulated secretion of ouabain exceeded the intracellular content of this steroid in either control or activated cells by 3-5 fold. The amount of angiotensin II stimulated ouabain secretion was greater from cells incubated in larger volumes. These results show that ouabain is enriched in the bovine adrenal cortex, and is secreted by primary cultures of these cells. The secretion of ouabain is increased by ACTH and angiotensin II, is due to either de novo synthesis or transformation of an intracellular precursor that is not overtly immunoreactive, and is feedback regulated by either ouabain itself or a cosecreted factor. These cells may be useful to study stimulus-secretion coupling and the biosynthetic pathway of ouabain.