Comparative in vitro percutaneous absorption of nonylphenol and nonylphenol ethoxylates (NPE-4 and NPE-9) through human, porcine and rat skin

Abstract

The purpose of this study was to assess the percutaneous absorption of nonylphenol (NP) and the nonylphenol ethoxylates, NPE-4 and NPE-9, in human, porcine and rat skin. In vitro studies with the NPEs were conducted for 8 h in flowthrough diffusion cells using topical solutions of 0.1, 1.0 and 10% in PEG-400 or 1% in water (NPE-9 only). NP absorption was assessed as a 1% solution in PEG-400. All compounds were 14C ring-labeled and radioactivity in perfusate was monitored over time. Skin deposition was measured at the termination of the experiment. Absorption into perfusate and total penetration (compound absorbed plus compound sequestered in skin) were calculated. Absorption of NPE-4, NPE-9 and NP was similar across all species at less than 1% of the applied dose over 8 h. Penetration was generally below 5% of applied dose, the majority located in the stratum corneum. In all species and for both NPEs, the fraction of dose absorbed was highest for the lowest applied dose. Absorptions expressed as actual mass absorbed over 8 h were similar (approximately 0.3 microg/cm2) across all concentrations. Penetration, but not absorption, was greater from a water vehicle compared to a PEG-400 vehicle, particularly in rat skin. These studies suggest that NP, NPE-4 and NPE-9 were minimally absorbed across skin from all three species. Fractional absorption was concentration-dependent, making the actual absorbed flux constant across all doses.

Topical L-Ascorbic Acid: Percutaneous Absorption Studies

“…The tape strips were discarded. Studies have shown that tape stripping removes the stratum corneum layers (data not shown) and removes surface radioactivity of topically applied substances bound to the stratum corneum 20,21 . Full‐thickness 6 mm punch biopsy specimens of skin were taken and placed immediately into liquid nitrogen.…”

Environmental Levels of para -Nonylphenol Are Able to Affect Cytokine Secretion in Human Placenta

“…Human exposure to p -NP may occur by cutaneous absorption, ingestion of contaminated food or water, and inhalation (Guenther et al 2003; Monteiro-Riviere et al 2000). Several studies have shown that p -NP binds to both estrogen receptor isoforms (ERα, ERβ), competing with the natural estrogen 17β-estradiol (17β-E 2 ) (Kwack et al 2002; Soto et al 1995; White et al 1994), although with less potency (Blom et al 1998; Nagel et al 1997).…”

Biological Tools to Study the Effects of Environmental Contaminants at the Feto–Maternal Interface

“… 33 Human exposure to p -NP may occur by cutaneous absorption, ingestion of contaminated food or water, and inhalation. 34 , 35 Estrogenic activity of p -NP has been known since 1991 33 and reported in a number of in vitro 36 and in vivo studies. 37 Interestingly, studies in rats showed that maternal exposure to p -NP resulted in an increase in uterine calbinding-D 9k (CaBP-9k) mRNA and protein expression in maternal and neonatal uteri, suggesting its potential transfer through the placenta.…”