RESUMO
Ouabain or a closely related isomer, and 'ouabain-like compound' (OLC), has been identified in plasma, by Hamlyn et al., using several physico-chemical and biological methods. Using a radioimmunoassay, the same authors later characterized an identical compound in adrenal cortex tissue and culture medium from adrenocortical cells. Nevertheless, other groups, using different immunosera, were not able to detect OLC in adrenal cortex and adrenocortical cells medium. In this report, we confirm the presence of OLC in bovine adrenal cortex and in fasciculata cells culture medium. The compound that we obtained has the same chromatographic properties as ouabain on HPLC using two types of elution systems. It presents the same mass spectrum and is able to bind to erythrocytes membranes Na(+)-K(+)-ATPase. In primary cultures of adrenocortical cells, its biosynthesis is increased after addition of pregnenolone or progesterone suggesting that these compounds may represent intermediate substrates in the biosynthetic pathway. Rhamnose readily enters the adrenocortical cell and increases slightly the biosynthesis of OLC. The present studies confirm that bovine adrenocortical cells in primary culture release an OLC with no differences with authentic ouabain using, HPLC, mass spectrometry and radioreceptor assay and suggest that OLC may be a product related to the adrenocortical steroidogenic pathway.
