F.J. Koschier1, R.N. Roth1, K.A. Wallace1, R.D. Curren2, J.W. Harbell2. 1ARCO, Los Angeles, CA, 2Microbiological Assoc., Inc., Rockville, MD.

The in vitro evaluation of the dermal irritation potential of volatile or water insoluble petroleum products has generally proved difficult. Scientists at ARCO and Microbiological Associates utilized three human skin constructs (Living Skin Equivalent [LSE], Organogenesis, Inc., Cambridge, MA; Skin2 Model ZK1300, Advanced Tissue Sciences, La Jolla, CA; and EpiDerm™, MatTek Corporation, Ashland, MA) to assess the dermal irritation potential of 14 petroleum refinery stream materials (10 for the LSE). The three constructs were not tested concurrently, but the test materials were taken from reference stocks to assure uniformity. Tissues were treated with the neat test materials for periods of up to 24 hours using the general dosing procedures recommended by the manufacturers. Certain modifications to the procedures were required to address the solvent characteristics and volatile nature of the test materials. After dosing, the tissues (in 6-well plates) were placed into heat-sealable plastic bags to prevent cross contamination between test articles. Four end points were assessed at each exposure time. The tissues’ viability was determined by both relative MTT conversion and LDH release. Culture medium under the tissue was also sampled for IL-1α and PGE-2 concentrations. The ET-50 (time to reduce the MTT conversion to 50% of time matched controls) was calculated for each test material in each system. In general, all three skin models ranked the test materials in a similar order of toxicity (ET-50), which was also similar in their PDII ranking. Spearman rank order analysis was LSE (0.54), ZK1300 (0.41) and EpiDerm (0.79). The actual ET-50’s of the more irritating materials varied somewhat between the three systems with toxicity occurring most quickly in the ZK1300 system. LDH release in the three systems corroborated cytoxicity estimated by the MTT-50. Cytokine levels were normalized to the ET-50 time point. These data indicated that PGE-2 levels were not very predictive of the known in vivo irritation level, but that IL-1α concentrations showed reasonable correlations, especially in the EpiDerm cultures. It appeared that for all three models the best prediction of in vivo irritation came from a combination of cytoxicity and IL-1α release measurements. Materials which had a very low in vivo irritancy (PDII24 hours and released no measurable IL-1α. Materials with moderate in vivo irritancy levels (1< PDII 24 hours but did show some release of IL-1α. Materials with even higher irritancy (PDII>4) caused marked cytoxicity and cytokine release.


Contact dermatitis, Cutaneous irritancy, Cutaneous irritation, Cutaneous toxicity, Cytokines, Dermal irritancy, Dermal irritancy testing, Dermal irritation, Endpoints, IL-1a, Endpoints, LDH, Endpoints, MTT, EpiDerm, IL-1a, Interleukin (IL), LDH, MTT, MTT ET-50 tissue viability assay, MTT assay, Petroleum products, Skin irritancy, Skin irritation, Skin models, cultured, Tween, Viability

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