A review of the bioavailability of petroleum constituents

Exposure to petroleum constituents at contaminated sites may occur through a variety of pathways, including inhalation of vapors and particulates, ingestion of water and soils, and dermal contact with water and soils. Accurately assessing the human health risks from such exposures requires information on the medium‐ and route‐specific bioavailability of petroleum constituents (e.g., how well these chemicals enter the body via the gastrointestinal tract and skin). For example, when the medium or exposure route in an animal toxicity assay (e.g., ingestion of water) differs from the actual route of human exposure at the petroleum contaminated site (e.g., dermal contact with soil), adjustments should be made that reflect the relative bioavailability of the chemical in the different media. The focus of this article is on (1) the availability of oral and dermal absorption data for one PAH (benzo[a]pyrene, (B[a]P) and three VOCs in soil (benzene, toluene, and xylene); (2) factors affecting the uptake of these PAHs and VOCs from soil; and (3) ways to incorporate bioavailability data into human health risk assessments. Based on our review, we recommend the following default values for the oral and dermal absorption of B[a]P, benzene, toluene, and xylene from soil:

A review of the bioavailability of petroleum constituents

All authors

Jennifer Bramard & Barbara D. Beck

https://doi.org/10.1080/15320389209383417

Published online:

02 December 2008

Display Table

Site‐specific information such as chemical concentrations in soil, soil characteristics, soil loadings on the skin, contact site, and contact time could result in modifications of these numbers. As shown, our default absorption values are generally less than those recommended by the U.S. EPA (1991a,b,c). The implications of these estimates of bioavailability for risk assessment and for the selection of soil cleanup levels at petroleum‐contaminated sites are discussed.     

Identification of N- and C-terminal corticotropin peptides in the Mr 80000 form of neurophysin

The 125I-labeled Mr 80000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1-39 adrenocorticotropin. The ACTH peptides 22-39 and 1-8, as well as the 1-7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high Mr neurophysin may contain the sequence of ACTH.     

Further characterization of the aggregation and fusion of chromaffin granules by synexin as a model for compound exocytosis

Synexin was isolated from bovine liver and found to aggregate adrenal chromaffin granules in the same Ca2+-dependent manner as previously described for adrenal synexin. The chromaffin granule aggregating activity of liver synexin was blocked in vitro by the addition of an antibody prepared to the 47,000 molecular weight band extracted from an SDS gel of an adrenal medullary synexin preparation. Chromaffin granules aggregated by synexin fused when exposed to cis-unsaturated fatty acids at concentrations comparable to those released from phospholipids by stimulated secretory cells. The synexin-induced aggregation reaction was blocked by Erythrosin B, a common food coloring, and by the phenothiazine antipsychotic trifluoperazine and promethazine. The aggregation and fusion of chromaffin granules thus appears to be a useful model system for studying synexin from diverse tissues and for testing pharmacologically or toxicologically active substances for effects on secretory systems.     

A comparison of aflatoxin B1-induced cytotoxicity,mutagenicity and prophage induction in Salmonella typhimurium mutagen tester strains TA1535, TA1538, TA98 and TA100

Treatment of Ames mutagen tester strains with aflatoxin B1 (AFB1) and S9 mix results not only in the production of a poten mutagen, but induces a pathway that leads to the induction of prophages present in all Ames tester strains.Characterization of the prophage induction and mutagenic response following AFB1 treatment showed that plasmid pKM101 dramatically enhances mutagenesis, but suppressed prophage induction. Spontaneous release of phage by TA98 and TA100 was also lower than in TA1535 and TA1538.In addition to mutagenesis and prophage induction, survival of all 4 tester strains was quantitated after AFB1 treatment. The data show that the frameshift tester strains (TA1538 and TA98) are more sensitive to the bactericidal action of AFB1 than the base-pair tester strains (TA1535 and TA100), survival being significantly affected above 100 ng. One of several hypotheses examined was the difference in the number and types of prophages present in base-pair tester strains that are not detectable in the frame-shift tester strains.These data suggest that prophage induction can detect DNA damage that is non-mutagenic; and that it is important to characterize the lysogenic nature of the Ames strains since it may influence the observed histidine revertant rate and the survival of the tester strain.     

Seven sesquiterpene lactones from Inula britannica var. chinensis

Four known sesquiterpene lactones, tomentosin, ivalin, 4-epi-isoinuviscolide and gaillardin, together with three new lactones, inuchinenolides A, B and C, were identified in the whole plant of Inula britannica var. chinensis.     

Regulation of Adenosine-Sensitive Adenylate Cyclase from Rat Brain Striatum

An adenosine-sensitive adenylate cyclase has been characterized from rat brain striatum. In whole homogenates as well as in particulate fractions, N⁶-phenylisopropyl adenosine (PIA), 2-chloroadenosine, and adenosine N′-oxide were equipotent in stimulating adenylate cyclase. Although GTP inhibited basal as well as PIA-stimulated activity of whole homogenates, the enzyme showed an absolute dependency on GTP for stimulation by PIA, dopamine, epinephrine, and norepinephrine in a particulate fraction derived from discontinuous sucrose gradient centrifugation. Adenosine exerts two effects on this adenylate cyclase, stimulation at low concentrations and inhibition at high concentrations, suggesting the presence of two adenosine binding sites. The stimulation of adenylate cyclase by PIA was dependent on the concentration of Mg^2-. The degree of stimulation by PIA was greater at a low concentration of Mg²⁺, which suggests that stimulation by PIA was accompanied by increasing the apparent affinity for Mg²⁺. Activation of adenylate cyclase by PIA was blocked by theophylline or 3-isobutyl- 1-methylxanthine (IBMX). The pH optimum for basal or (PIA + GTP)-stimulated activities was broad, with a peak between 8.5 and 9.5. In the presence of GTP, stimulation by an optimal concentration of PIA was additive, with maximal stimulation by the catecholamines. Phospholipase A₂ treatment at a concentration of 1 U/ml for 5 min completely abolished the stimulatory effect of dopamine, whereas PIA-stimulated activity remained unaltered. These data suggest that rat brain striatum either has a single adenylate cyclase, which is stimulated by catecholamines and adenosine by distinct mechanisms, or has different cyclase populations, stimulated by either adenosine or catecholamines.