Effect of Cold Storage on In Vitro Human Skin Absorption of Six ¹⁴C-Radiolabeled Environmental Contaminants: Benzo[a]Pyrene, Ethylene Glycol, Methyl Parathion, Naphthalene, Nonyl Phenol, and Toluene

Abstract

Dermal absorption of human breast skin obtained fresh from a local hospital was tested before and after freezer storage at –19°C for 30 or 60 d. Dermatomed skin (0.4–0.5 mm) was tested in vitro using the Bronaugh flow-through diffusion cells perfused at 1.5 ml/h with receiver solution (Hanks HEPES buffered basal saline containing 4% bovine serum albumin [BSA]). Six ¹⁴C-radiolabeled chemicals ranging in lipophilicity were tested, including benzo[a]pyrene (BaP), ethylene glycol (EG), methyl parathion (MP), naphthalene (Nap), nonyl phenol (NP), and toluene (Tol). There was significantly lower percent dermal absorption into the receiver solution for two of the six chemicals (BaP and Tol) with the skin depot excluded. However, with percent dermal absorption defined as that including the skin depot, with the exception of the BaP data for skin frozen 30 d, there was no significant difference between percent dermal absorption data for fresh unfrozen controls and those stored frozen for all 6 test chemicals for both 30 and 60 d freezer storage times. These results suggested with skin depot included that freezer storage may have potential for preserving human skin for in vitro absorption tests of environmental contaminants; however, optimal freezer storage conditions such as temperature and storage duration and their effects on skin viability and dermal metabolism need to be determined.

This study was approved by the Ottawa Hospital Research Ethics Board (REB) and by Health Canada REB. We thank the patients who kindly donated surgical waste skin tissues and Dr. Murray Allen, Dr. Michael Bell, and staff of the Ottawa Hospital and Dr. Sam Kacew, University of Ottawa Medical School. We thank Pat Goegan and Dr. Jamie Nakai for extensive in-house review of this article. We also thank Hart MacPherson, New Chemicals Division, Substances Assessment and Control Bureau, and Dr. Mark Richardson, Bureau of Risk and Impact Assessment, for support. We also thank Dr. Ken Storey, Carleton University (Ottawa, ON) for helpful discussion early on in this project. Statistical advice from Dr. Andrew Williams, Health Canada, Biostatistics and Epidemiology Division, was much appreciated.