Regulation of lithium and boron levels in normal human blood: environmental and genetic considerations.

Blood lithium levels may be both genetically and environmentally regulated. The genetic component is evidenced mainly from studies in twins who were either normal or had a manic-depressive disorder. An environmental contribution is adduced from the relationship between the blood lithium level and the amount of the element ingested. No such information is available for boron, another element present in ultra trace amounts in human blood. Unusually high levels of lithium and boron in the waters of northern Chile offer an opportunity to study the genetic and environmental regulation of these elements in the blood of healthy subjects. Samples of blood (n = 40) and water (n = 47) were collected at seven locations in the province of Tarapaca. Most of the healthy subjects were Aymara who had been resident in the respective communities for at least 3 years. The samples were transported to Canada and then freeze-dried. Neutron irradiation was performed in a highly thermalized flux to induce the reactions 6Li (n, alpha) t and 10B (n,7Li) alpha. Assays of 6Li and 10B were conducted in a static mass spectrometer by measurement, respectively, of 3He, produced from decay of tritium, and 4He from alpha-particles. Lithium concentrations in water and blood exhibited a linear relationship, as did the boron concentrations in these fluids. Because some of the individual subjects (n = 15) were first-degree relatives, a genetic component to the regulation of blood levels was explored. The variance in blood levels of lithium and boron was significantly greater between than within families (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)