Has the elusive "natriuretic factor" been discovered, and if so, is it a hormone?

This review summarizes the interesting and significant papers reported at the International Conference on Natriuretic and Digitalis-like Factors held at the ASH meeting in San Francisco, June 1-2, 1997. This area of investigation has been rejuvenated as of late with near structural determination of two ouabain-like isolates from human plasma (OLF) and bovine hypothalamus (HIF) which are apparently the same compound and the isolation and structural elucidation of a natriuretic metabolite of gamma-tocopherol. Spectroscopic information has also been obtained for two other compounds, an ouabain-like factor from bovine adrenals and HHIF from the hypothalamus. An explanation was offered for how low concentrations of digitalis-like factors can regulate vascular reactivity when the predominant isoform of the sodium pump has a low affinity for these compounds. Various groups are examining possible in vivo synthetic pathways that could lead to the production digitalis-like factors. The natriuretic metabolite of gamma-tocopherol, LLU-alpha, fits deWardener's postulates for a natriuretic hormone and is being examined for its involvement in ECF control. Once the structures for some of these ouabain-like compounds are determined and they are synthesized, these compounds will also be able to be studied employing classical pharmacologic methods.