sodium-nitrite and sodium-thiocyanate

The binding of aqueous anions (ClO4-, SCN-, I-, and NO3-) to lipid bilayer membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was investigated using deuterium (2H) and phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectroscopy. The ability of these anions to influence the 2H NMR quadrupole splittings of POPC, specifically labeled at the alpha or beta position of the choline head group, increased in the order NO3- much less than I- less than SCN- less than ClO4-. In the presence of these chaotropic anions, the quadrupole splitting increased for alpha-deuterated POPC and decreased for beta-deuterated POPC, indicating a progressive accumulation of negative charge at the membrane surface. Calibration of the 2H NMR quadrupole splittings with the amount of membrane-bound anion permitted binding isotherms to be generated for perchlorate, thiocyanate, and iodide, up to concentrations of 100 mM. The binding isotherms were analyzed by considering electrostatic contributions, according to the Gouy-Chapman theory, as well as chemical equilibrium contributions. For neutral POPC membranes, we obtained ion association constants of 32, 80, and 115 M-1 for iodide, thiocyanate, and perchlorate, respectively. These values increase in the order expected for a Hofmeister series of anions. We conclude that the factor determining whether a particular anion will bind to lipid bilayers is the ease with which that anion loses its hydration shell.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Anions; Binding Sites; Deuterium; Lipid Bilayers; Magnetic Resonance Spectroscopy; Osmolar Concentration; Phosphatidylcholines; Sodium Hypochlorite; Sodium Iodide; Sodium Nitrite; Thiocyanates

Sodium thiocyanate, a common environmental chemical, was found to increase the incidence of liver tumors in a group of rats treated with 0.08% in drinking water. To test the possibility that thiocyanate was catalyzing the formation of carcinogenic nitrosamines from amines and nitrite in the food, a group of 20 male and 20 female rats was given a higher dose of sodium thiocyanate (0.32%) together with sodium nitrite (0.2%) in drinking water. Similar groups of rats were given 0.32% sodium thiocyanate or 0.2% sodium nitrite in drinking water or were untreated. All treatments lasted most of the lifetime of the rats, at least 2 years. There was no difference between the groups, treated or untreated, in survival, or in the incidence of any tumor that could be related to the treatment. The results indicate that sodium thiocyanate is without carcinogenic activity in rats, alone or combined with sodium nitrite.

Topics: Animals; Female; Leukemia, Experimental; Liver Neoplasms, Experimental; Male; Nitrites; Rats; Rats, Inbred F344; Sodium Nitrite; Thiocyanates

Isolated frog gastric mucosa was used to study the separation of formation of protons (or their precursors) from proton translocation by using various inhibitors. Both thiocyanate (SCN-) and nitrite (NO2-) inhibit the acid secretion in spontaneously secreting mucosa. The inhibition is reversed when the inhibitor is removed such that the excess acid secreted above baseline in the 'off'-period compensates for the amount inhibited in the 'on'-period. Both agents also inhibit the effect on acid secretion of pulse stimulation with histamine though to a lesser extent. Upon removal of the inhibitor, the total amount of acid secreted in excess of basal is equal to that observed with histamine alone. Likewise, metiamide, an H2-antagonist, also inhibits acid secretion with or without histamine. However, in contrast to SCN- and NO2-, removal of this inhibitor is without effect on the acid-secretion rate. These results indicate that both SCN- and NO2- inhibit the proton translocation rather than the formation of protons or their precursors as is the case with metiamide.

Topics: Animals; Cyclic AMP; Gastric Acid; Gastric Mucosa; Histamine; Kinetics; Metiamide; Nitrites; Rana catesbeiana; Sodium Nitrite; Thiocyanates