A preliminary study of the dermal absorption of aluminium from antiperspirants using aluminium-26

Aluminium chlorohydrate (ACH), the active ingredient in many antiperspirants, was labeled with the radioisotope 26Al. The labeled ACH was then fractionated into about 100 samples using gel filtration chromatography. Each fraction was analyzed for 26Al and total aluminium content. Aluminium-26 was only detected in the fractions that also contained aluminium, which verified that the ACH was uniformly labeled. 84 mg of the labeled ACH was then applied to a single underarm of two adult subjects with blood and urine samples being collected over 7 weeks. Tape-stripping and mild washings of the skin were also collected for the first 6 days. Results indicate that only 0.012% of the applied aluminium was absorbed through the skin. At this rate, about 4 microg of aluminium is absorbed from a single use of ACH on both underarms. This is about 2.5% of the aluminium typically absorbed by the gut from food over the same time period. Therefore, a one-time use of ACH applied to the skin is not a significant contribution to the body burden of aluminium.

Adsorption of esters of p-hydroxybenzoic acid by filter membranes: mechanism and effect of formulation and processing parameters

The adsorption of esters of p-hydroxybenzoic acid (parabens) by filter membranes was studied by a flow-through technique. The hydrophobic effect was the major mechanism of adsorption. Propylparaben was more extensively adsorbed by all the membranes than was methylparaben. Hydrophobic membranes exhibited the greatest degree of adsorption, whereas adsorption was minimal for hydrophilic membranes. The charge of the filter membrane did not affect paraben adsorption. Formulation factors studied included the concentration of paraben, the presence of a tonicity-modifying agent (sodium chloride, mannitol, glycerin), and the presence of a chelating agent (edetate sodium). Paraben adsorption was directly related to paraben concentration. The presence of a tonicity modifier or chelating agent did not alter paraben adsorption to membrane filters. Processing parameters studied included flow rate, temperature, autoclaving, flow interruption, and filter membrane presaturation. Presaturation of the filter membranes for up to 1 hr reduced but did not eliminate paraben adsorption during simulated use. Interrupting the flow of the paraben solution through the filter membrane allowed for additional paraben adsorption and caused the concentration of paraben in the restarted filtrate to be less than 100% of theory.

Adsorption of benzalkonium chloride by filter membranes: mechanisms and effect of formulation and processing parameters

The purpose of this study was to elucidate the mechanism(s) of adsorption of benzalkonium chloride (BAK) by filter membranes and to determine the effect of formulation and processing parameters on the adsorption of BAK. Six different sterilizing grade filter membranes were used in this study. Adsorption was monitored by passing an aqueous solution of BAK at pH 6 through a 47-mm (14.2 cm2 effective filter area) disk filter membrane and measuring the UV absorption of the filtrate with a UV micro flow cell. Hydrophobic and/or electrostatic forces were chiefly responsible for adsorption. The adsorption properties of each filter membrane could be related to its composition. Membranes that were hydrophilic and nonionic or hydrophilic and cationic adsorbed little BAK. However, membranes that were hydrophobic or anionic exhibited significant BAK adsorption. Adsorption followed the Langmuir equation and adsorptive capacities ranged from 116 to 429 micrograms/47 mm membrane (8.17-30.23 micrograms/cm2). Formulation factors studied included the concentration of BAK, the presence of a tonicity-modifying agent (sodium chloride, mannitol, glycerin), and the presence of a chelating agent (edetate disodium). The greatest increase in adsorption of BAK occurred when sodium chloride or edetate disodium was used with membranes that contained cationic sites. The effects of flow rate, temperature, autoclaving, interrupting the flow, and presaturating the filter membrane were the processing parameters studied. The rate of adsorption was inversely related to flow rate and the extent of adsorption was inversely related to temperature. Presaturation of the filter membrane with BAK was an effective method to reduce the adsorption of BAK during filtration.

Agonist-induced down-regulation of alpha(1B)-adrenergic receptor in HEK293 cells transfected with alpha(1B) cDNA

HEK293 cells stably expressing hamster alpha(1B)-adrenergic receptor (alpha(1B)-AR) were used to observe the effect of nonepinephrine (NE) on alpha(1B)-AR gene expression. Radioligand binding assys and RNase protection assays were used to determine alpha(1B)-AR number and the mRNA level, respectively. Exposure (2-24 h) of HEK293 cella to NE (10 mumol) caused a decrease in alpha(1B)-AR mRNA with maximum change found at the 4th hour. and in alpha(1B)-AR density at the 24th hour. NE-induced decrease in alpha(1B)-AR mRNA was inhibited by protein kinase C (PKC) inhibitor calphostin C (0.1. mumol) and mimicked by PKC activator PMA (1 mumol). Nuclear run-off transcription assay showed that treatment of the cells with NE (10 mumol) exerted no effect on the transcription rate of alpha(1B)-AR, After the synthesis of new RNAs was inhibited by actinomycin D, NE muld not accelerate the degradation of alpha(1B)-AR mRNA. The results suggested that in the HEK293 cells NE muld induce the down-regulation of alpha(1B)-AR, and the effects were mediated by PKC pathway. NE could not alter the transcription rate of alpha(1B)-AR mRNA, but it might induce the synthesis of some factors and indirectly accelerate the degradation.

Use of bacterial photosynthetic vesicles to evaluate the effect of ionic liquids on the permeability of biological membranes

Ionic liquids (ILs) are salts composed of a combination of organic or inorganic cations and anions characterized by a low melting point, often below 100 °C. This property, together with an extremely low vapor pressure, low flammability and high thermal stability, makes them suitable for replacing canonical organic solvents, with a reduction of industrial activities impact on the environment. Although in the last decades the eco-compatibility of ILs has been extensively verified through toxicological tests performed on model organisms, a detailed understanding of the interaction of these compounds with biological membranes is far from being exhaustive. In this context, we have chosen to evaluate the effect of some ILs on native membranes by using chromatophores, photosynthetic vesicles that can be isolated from Rhodobacter capsulatus, a member of the purple non‑sulfur bacteria. Here, carotenoids associated with the light-harvesting complex II, act as endogenous spectral probes of the transmembrane electrical potential (ΔΨ). By measuring through time-resolved absorption spectroscopy the evolution of the carotenoid band shift induced by a single excitation of the photosynthetic reaction center, information on the ΔΨ dissipation due to ionic currents across the membrane can be obtained. We found that some ILs cause a rather fast dissipation of the transmembrane ΔΨ even at low concentrations, and that this behavior is dose-dependent. By using two different models to analyze the decay of the carotenoid signals, we attempted to interpret at a mechanistic level the marked increase of ionic permeability caused by specific ILs.