Acute and chronic effects of carbon monoxide on mitochondrial function.

The purpose of the present study was to examine whether there were some differences between metabolic responses induced by carbon monoxide (CO) poisoning and those by hypoxic hypoxia. Significant decrease in cytochrome oxidase (COX) activity in heart and liver was observed during acute exposure, while no change was observed in brain. When the control of respiration was investigated, cerebral energy homeostasis was maintained even after severe exposure. In order to document this phenomenon we measured blood flow in liver and brain, but increase in cerebral blood flow was not observed and the experiments failed to show a relationship between cerebral homeostasis and blood flow. The prolonged exposure to CO and hypoxia resulted in an increase in COX and these responses were obviously considered to be adaptive to chronic exposure. From the results of acute and chronic exposure it is considered to be difficult to determine if CO has the direct effect on the respiratory chain. Further studies of the mechanism of the CO toxicity may be necessary.

Enhanced binding of morphine and nalorphine to opioid delta receptor by glucuronate and sulfate conjugations at the 6-position.

Effect of the modification of morphine and nalorphine by glucuronate and sulfate conjugations at the 3- and 6-positions on the binding to opioid receptors was examined in a particulate fraction of rat brain. Competing potencies of both drugs against [3H]morphine and [3H]leucine enkephalin bindings were extremely decreased by either glucuronate or sulfate conjugation at the 3-position. On the other hand, the potencies of morphine and nalorphine against [3H]leucine enkephalin binding were considerably enhanced by the conjugations at the 6-position, whereas the potencies against [3H]morphine binding were decreased. These altered interactions of the conjugates at the 6-position with the two ligands were attributed to their enhanced binding to delta-receptor and reduced binding to mu-receptor by Hill plot and modified Scatchard analysis. Resulted comparable and simultaneous interactions with mu- and delta- receptors were assumed to be a cause of the enhanced mu-receptor-directed analgesia of morphine and elevated same receptor-directed antagonistic effect of nalorphine, which have been found previously in our laboratory.

Potentiation of physical dependence by conjugation at the 6-position of nalorphine.

The experiments concerned the effects of glucuronate or sulfate conjugation at the 6-position of nalorphine on the analgesic and antagonistic activities and also on the development of tolerance and physical dependence. Nalorphine-3-and 6-sulfate ester were synthesized for the first time. The analgesic effect of nalorphine-6-sulfate and -glucuronide was higher than that of nalorphine when assessed in the acetic acid writhing test. However, these 6-conjugates exhibited less potent agonistic activity in the test with guinea-pig ileum muscle strip and revealed no analgesic effect in the tail pinch test. The antagonistic activity of these 6-conjugates to morphine analgesia was lower on their s.c. injection, but higher on i.c.v. injection than that of nalorphine. The development of tolerance to the analgesia caused by nalorphine was not affected by the 6-modifications. Frequent withdrawal signs were seen in mice treated chronically with anlorphine-6-conjugates by challenging with naloxone while mice treated with nalorphine showed no such signs. This potent enhancing effect of 6-conjugation on the development of physical dependence was suggested to be also the case with morphine. These changes of potency due to conjugation were interpreted as due to the altered interaction with multiple opioid receptors.

[Effect of heating on COHb% of the blood].

The blood from burned cadavers heat-coagulates badly and COHb% at autopsy is expected to be lower than that at death. To study such an effect of heating on COHb% in the blood, we have carried out experiments on heating of dead bodies of CO intoxicated guinea pigs as well as that of blood containing COHb in vitro. Three high temperatures (300 degrees C, 500 degrees C, 700 degrees C) and five exposure times (5 min, 10 min, 15 min, 20 min, 30 min) were used to stimulate conditions of real fire. Supposing that the effect of heat can be expressed in terms of a product of heating temperature with exposure time, a relation between the product and CO liberation rate was examined. The release of CO is at most 20% of the CO initially present when the product is under 5,000 and the blood retains still fluid, whereas the release of CO is about 50% when the product is over 10,000 and the blood is clotted. It is difficult to adapt CO release from COHb observed in experiments on heating in vitro and in the dead body to the judgment of the causes of death of burnt corpses, but if taking into consideration the degree of burns of charred bodies and the degree of the heat coagulation of the blood, it is suggested that one is able to anticipate COHb% at death from the gas chromatographic measurement of COHb% at autopsy in medico-legal practice.