Mechanisms of petroleum hydrocarbon toxicity: functional changes in rat liver mitochondria after exposure to a Prudhoe Bay Crude Oil

Toxicological Effects of Inhaled Crude Oil Vapor

PURPOSE OF REVIEW

The purpose of this review is to assess the toxicological consequences of crude oil vapor (COV) exposure in the workplace through evaluation of the most current epidemiologic and laboratory-based studies in the literature.

RECENT FINDINGS

Crude oil is a naturally occuring mixture of hydrocarbon deposits, inorganic and organic chemical compounds. Workers engaged in upstream processes of oil extraction are exposed to a number of risks and hazards, including getting crude oil on their skin or inhaling crude oil vapor. There have been several reports of workers who died as a result of inhalation of high levels of COV released upon opening thief hatches atop oil storage tanks. Although many investigations into the toxicity of specific hydrocarbons following inhalation during downstream oil processing have been conducted, there is a paucity of information on the potential toxicity of COV exposure itself. This review assesses current knowledge of the toxicological consequences of exposures to COV in the workplace.

Functional and ultrastructural cell pathology induced by fuel oil in cultured dolphin renal cells

Investigations were undertaken to elucidate in a marine mammal renal cell culture system the toxicity and some of the mechanisms of cytopathology in a standardized preparation following exposure to No. 1 fuel oil. Cell survivability of a cultured SP1K renal cell line from the Atlantic spotted dolphin Stenella plagiodon was reduced in a dose-dependent manner after a 12-h exposure to fuel oil. Early morphologic changes reflecting cytotoxicity, as revealed by transmission electron microscopy, included enlarged rough endoplasmic reticula, cytoplasmic vacuolization, and degenerative cytoplasmic inclusions, but mitochondria remained resistant. Assessment of extracellular proton loss by microphysiometry of cultured cells revealed fuel oil-induced enhancement of proton loss that was dependent upon both protein kinase C and renal epithelial Na(+)/H(+) counter-transport functioning, as the specific inhibitors H-7 and amiloride reduced this stimulatory petroleum effect. Cell cycle progression and apoptosis (programmed cell death) were studied in dolphin renal cells exposed to fuel oil for 12, 24, and 48 hours. The toxicant increased the percentage of cells in GO/GI phase and decreased the percentage of cells in S phase starting after 24 hours. The number of cells undergoing early apoptosis was also increased after 24 hours.

Developmental toxicity of carbon black oil in mice

BACKGROUND

Carbon black oil (CBO) is a refinery side-stream product used to produce asphalt and other commercial products. CBO contains several classes of hydrocarbons, several of which are known to exhibit systemic and gestational toxicities, making this mixture a candidate for causing reproductive toxicity.

METHODS

Swiss-Webster mice were administered CBO (300, 350, 400 mg/kg/day) via oral gavage in a dosage volume of 10 microl/g body weight on gestation days (GD) 6-15. Uterine contents were evaluated on GD 18.

RESULTS

Treatment with CBO at all dosage levels resulted in a high frequency of maternal clinical symptoms and a decrease in maternal weight gain. Decreased fetal viability was observed, manifested as a decrease in viable implants and, in a high percentage of treated dams, as early resorption of the entire litter. A significant reduction in fetal weight was also observed. However, neither structural malformations nor developmental delays in ossification were observed in any of the living offspring. To minimize maternal toxicity, the dosage range was lowered (100, 200, 300 mg/kg/day), and the concentration was adjusted such that the volume administered to each dam was decreased by 20%. In this trial, the only maternal effect observed was an increase in maternal liver weight at 200 and 300 mg/kg. The fetal lethality effects observed previously were reduced substantially. Nevertheless, the frequency of resorption among all treatment groups was higher statistically than in controls.

CONCLUSIONS

These data support the hypothesis that CBO is reproductively toxic in Swiss-Webster mice at oral doses of >/=100 mg/kg/day.

Effects of ingested crude oil on thyroid hormones and on the mixed function oxidase system in ducks

1. Ingestion of Statfjord A crude oil from the North Sea has no apparent effect on the metabolic rate of ducks (Jenssen, 1989). This may be because this particular oil does not affect plasma concentrations of thyroid hormones and enzyme activities in the mixed function oxidase (MFO) system of ducks. 2. To test this hypothesis, plasma concentrations of thyroid hormones (thyroxine and triiodothyronine), and levels of hepatic cytochrome P-450 and enzyme activities (NADPH cytochrome C reductase and GSH-S-transferase) in the MFO system were measured in domestic ducks (Anas platyrhynchos) which had ingested this crude oil. 3. Daily oral of 5 ml crude oil per kg body weight for 6 consecutive days resulted in a 53% increase in plasma triiodothyronine concentration and a 56% increase in the hepatic cytochrome P-450 level. The changes in these parameters were apparently not sufficient to cause any rise in metabolic heat production. 4. This apparent contradiction is probably because activation of the MFO-system is energetically inexpensive. Also, possible metabolic effects caused by increased plasma-triiodothyronine concentration and activation of the MFO-system may have been masked by an inhibitory effect of the crude oil on mitochondrial electrontransport and coupled phosphorylation.

Comparison of the inhibitory effects of some compounds present in crude oils on rat platelet aggregation: role of intra- and extra- cellular calcium

In vitro addition of some representative aliphatic, aromatic or heterocyclic compounds present in petroleum crude oils to washed rat platelets resulted in a concentration-dependent inhibition of aggregation induced by ADP or thrombin. Increasing concentration of extracellular Ca2+ did not alter the pattern of inhibition. ADP-induced intracellular Ca2+ mobilization was unaffected by most of the compounds tested. However, Ca2+ uptake was significantly inhibited when platelets were preincubated with these agents. This suggests that some components of crude oil may inhibit platelet aggregation by bringing about alterations in the platelet plasma membrane.

The hepatotoxic potential of a Prudhoe Bay crude oil: effect on mouse liver weight and composition

The hepatotoxic properties of a Prudhoe Bay Crude Oil (PBCO) were evaluated in mice. Administration of PBCO (5.0 ml/kg body wt, daily for 2 days) to mice resulted in an increase in (i) liver wet and dry weight, (ii) hepatic total proteins, RNA, glycogen and total lipids, and (iii) individual lipids such as cholesterol, triglycerides and phospholipids. Hepatic protein biosynthesis, determined in vivo by administration of L-[14C]leucine was increased in PBCO exposed mice. The rate of 3H incorporation from 3H2O was significantly enhanced in liver fatty acids, cholesterol, triglycerides and thus ultimately in total lipids. Also, an increase in 3H incorporation was noticed in hepatic glycogen after PBCO administration. The results suggest that PBCO may induce hepatotoxicity by altering the intermediary metabolism of biochemical constituents.

Mechanisms of petroleum hydrocarbon toxicity: destruction of liver microsomal and mitochondrial calcium pump activities by a Prudhoe Bay crude oil

Administration of Prudhoe Bay crude oil (PBCO) to rats resulted in an abrupt drop in liver mitochondrial and microsomal ATP-dependent calcium uptake activity. Also, in vitro incubations of either mitochondria or microsomes in the presence of a dimethyl sulfoxide (DMSO) extract of PBCO resulted in a dose-dependent inhibition of calcium influx. The release of calcium from calcium-loaded mitochondria and microsomes was also observed in the presence of the PBCO extract. At concentrations which effect calcium sequestration, the PBCO extract produced swelling of mitochondria. Microsomal ATPase activity in the presence or absence of calcium was unaffected by PBCO. The results indicate that increased permeability of the membranes to calcium is a contributory factor in the inhibition of calcium uptake by PBCO.