Certain hexavalent chromium (Cr^(6+)) compounds when administered via inhalation at high doses have the potential to induce lung tumors in humans and experimental animals. Trivalent chromium (Cr^(3+)) is an essential ...Certain hexavalent chromium (Cr^(6+)) compounds when administered via inhalation at high doses have the potential to induce lung tumors in humans and experimental animals. Trivalent chromium (Cr^(3+)) is an essential human and animal nutrient at levels of 50 to 200 μg/day. Recent data have shown that the human body is able to reduce Cr^(6+) to Cr^(3+). This reduction occurs in bodily fluids such as gastric juice, epithelial lining fluid of.the respiratory tract, blood, and other fluids. Secondary reduction occurs at the cellular level by the cytosol, mitochondria, and microsomes. Thus, at low levels of exposure hexavalent chromium ions are reduced befor the 6+ ions can interact with DNA unless the dose is sufficient to overwhelm the body's reduction capacity. This paper summarizes the available data concerning the reducing ability of the body and formulates the steps in the mechanism of cancer induction. These steps include: (1) only certain Cr^(6+) compounds have the capacity to interact with cellular components; (2) Cr^(6+) is reduced by body fluids and excess Cr^(6+) enters the cell (Cr^(3+) is poorly absorbed across membranes); (3) cellular organelles and the cytoplasm reduce Cr^(6+) to Cr^(3+); (4) excess Cr^(6+) can enter the nucleus; (5) Cr^(6+) reduction through 5+ and 4+ to 3+ has a potential to interact with the DNA molecule; and (6) if unrepaired, this DNA damage can lead to cancer induction. On the basis of current evidence Cr^(6+) has a threshold for carcinogenic potential in humans that is greater than the current TLV. 1990 Academic Press. Inc.展开更多
During a toxicological test using diisopropyl methylphosphonate (DIMP) on mallards, an anaesthesia-like response was noted after oral dosing. In order to further elucidate these effects, arterial blood pressures were ...During a toxicological test using diisopropyl methylphosphonate (DIMP) on mallards, an anaesthesia-like response was noted after oral dosing. In order to further elucidate these effects, arterial blood pressures were determined both pre-and post-dosing on adit male and female mallards by cannulation of the left carotid artery. A significant decrease in systolic, diastolic, and mean blood pressure was noted after the oral administration of DIMP. There was no significant difference in response between males and females. During the first 30 min after dosing, systolic pressure fell from an average of 158 mmHg, to 94 mmHg, diastolic decreased from 127 mmHg to 63 mmHg, and mean blood pressure dropped from 138 mmHg to 75 mmHg. However, there was no significant effect on pulse pressure, heart rate, or respiratory rate. These results are compared to physiological data cited in the literature for various CNS-acting drugs on mallards.展开更多
文摘Certain hexavalent chromium (Cr^(6+)) compounds when administered via inhalation at high doses have the potential to induce lung tumors in humans and experimental animals. Trivalent chromium (Cr^(3+)) is an essential human and animal nutrient at levels of 50 to 200 μg/day. Recent data have shown that the human body is able to reduce Cr^(6+) to Cr^(3+). This reduction occurs in bodily fluids such as gastric juice, epithelial lining fluid of.the respiratory tract, blood, and other fluids. Secondary reduction occurs at the cellular level by the cytosol, mitochondria, and microsomes. Thus, at low levels of exposure hexavalent chromium ions are reduced befor the 6+ ions can interact with DNA unless the dose is sufficient to overwhelm the body's reduction capacity. This paper summarizes the available data concerning the reducing ability of the body and formulates the steps in the mechanism of cancer induction. These steps include: (1) only certain Cr^(6+) compounds have the capacity to interact with cellular components; (2) Cr^(6+) is reduced by body fluids and excess Cr^(6+) enters the cell (Cr^(3+) is poorly absorbed across membranes); (3) cellular organelles and the cytoplasm reduce Cr^(6+) to Cr^(3+); (4) excess Cr^(6+) can enter the nucleus; (5) Cr^(6+) reduction through 5+ and 4+ to 3+ has a potential to interact with the DNA molecule; and (6) if unrepaired, this DNA damage can lead to cancer induction. On the basis of current evidence Cr^(6+) has a threshold for carcinogenic potential in humans that is greater than the current TLV. 1990 Academic Press. Inc.
文摘During a toxicological test using diisopropyl methylphosphonate (DIMP) on mallards, an anaesthesia-like response was noted after oral dosing. In order to further elucidate these effects, arterial blood pressures were determined both pre-and post-dosing on adit male and female mallards by cannulation of the left carotid artery. A significant decrease in systolic, diastolic, and mean blood pressure was noted after the oral administration of DIMP. There was no significant difference in response between males and females. During the first 30 min after dosing, systolic pressure fell from an average of 158 mmHg, to 94 mmHg, diastolic decreased from 127 mmHg to 63 mmHg, and mean blood pressure dropped from 138 mmHg to 75 mmHg. However, there was no significant effect on pulse pressure, heart rate, or respiratory rate. These results are compared to physiological data cited in the literature for various CNS-acting drugs on mallards.
