Carboxyhemoglobin Formation Research Articles

The path of an artificial earth satellite in the normal gravitational field of the earth

The 10- or 12-hr workday has become increasingly popular in industry. Current occupational exposure limits are designed to protect workers on the standard 8-hr/day workshift and are not intended for use for longer workshifts. Experiments were conducted to compare the effects of a 12-hr exposure schedule to those of an 8-hr schedule on the carboxyhemoglobin (COHb) formation resulting from dichloromethane (DCM) inhalation. Rats and mice were exposed to 200, 500, or 1000 ppm DCM for 8hr/day for 5 days or 12 hr/day for 4 days. The effect of the unusual exposure schedule on COHb levels was not significant. The metabolic pathway for the formation of COHb appeared to be saturated even at the lowest concentration of DCM. To examine the possible increase in the retention of inhaled DCM in the longer exposure schedule, single exposures for 8 and 12 hr were compared. The peak blood DCM level was dependent upon the DCM exposure concentration, but the half-life was independent of the duration of exposure and the concentration of DCM. The half-life of COHb in blood was prolonged by increasing the DCM concentration, but was not affected by the exposure period. Pyrazole treatment decreased COHb level and increased blood DCM level in rats exposed to DCM. These results suggest that the exposure limit for a chemical with a short biological half-life and readily reversible toxic effect may not need to be adjusted for a longer workshift which is in agreement with some of the mathematical models based upon the pharmacokinetics of a toxicant.

Protective Action of Carbon Monoxide in Mammalian Whole-Body X-Irradiation

Prophylactic and/or therapeutic agents combating the effects of ionizing radiation are naturally of great interest. Recently carbon monoxide has been reported (1, 2) as being a protector against X-irradiation. Bonet-Maury (2) believes that the carbon monoxide effect due to the formation of carboxyhemoglobin by the CO, leading to a reduced rate of oxygen from the lungs to the cells. Patt (3) reviews the many investigations on the relationship between oxygen and radiosensitivity. In this laboratory, protection from hypoxia significantly increased survival time of guinea pigs at all doses tested from 500 to 8000 r (4). Since carbon monoxide is another way of creating an hypoxia condition (5-7), the present study was designed to obtain (1) general information about the carbon monoxide effect when it is given before and/or after X-irradiation, and (2) specific information verified by statistical analysis.

Toxicology

Mechanisms of Poisonous Action Carbon Monoxide In man, the most simple mechanism of poisoning is that brought about by the inhalation of carbon monoxide. This gas, which is readily absorbed in the lungs, acts by interfering with the ability of the blood to transport oxygen to the tissues. It reversibly poisons the "fluid catalyst," hemoglobin, by forming a compound with it in competition with the compound formed by oxygen. The equilibrium favors the formation of carboxyhemoglobin over oxyhemoglobin by a factor of about 300:1, so that the arterial blood of a person remaining until equilibrium is established in an atmosphere . . .