Submitted to: Health Effects of Boron and Its Compounds International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: October 22, 1997
Publication Date: N/A
Technical Abstract: Vascular plants, diatoms, and some species of marine algal flagellates and nitrogen-fixing cyanobacteria have acquired an absolute requirement for boron. In biological systems, inorganic boron is thought to be essentially present only as the mononuclear species boric (orthoboric) acid [B(OH)3] which has an affinity for one to four suitable hydroxyl groups at physio- logical concentrations and pH. Because many biochemicals (e.g., NADPH an the serine proteases) contain these groups, numerous biological boron esters and complexes are possible. Stability of boron esters and complexes varies according to number of hydroxylic groups and the presence and nature of a third group in the molecule. This phenomenon provides the basis for a working hypothesis for at least one role of boron in humans and higher animals; boron reacts with certain enzymes or their co-factors to form easily reversible esters or complexes with dydroxyl groups and thereby dampens and regulates the activity of these enzymes. Direct evid- ence for this hypothesis comes from studies of plant, cell culture, and purified chemical reaction systems. Indirect evidence comes from whole animal studies where dietary boron reduced the incidence and severity of adjuvant-induced arthritis in rats, a finding consistent with the hypo- thesis that boron dampens the activity of certain key components of the respiratory burst. In chicks, boron reduced in situ pancreatic insulin re- lease after a glucose load, a finding that suggests boron dampens the activity of the voltage-dependent Ca**2+ channel by reducing NADPH concen- trations and thence, insulin release. Further characterization of the re- lation between boron and certain enzymes will involve measurement of enzy- matic processes most likely affected by physiological amounts of boron.