Ionic copper entering blood plasma binds tightly to albumin and the macroglobulin transcuprein. It then goes primarily to the liver and kidney except in lactation, where a large portion goes directly to the mammary gland. Little is known about how this copper is taken up from these plasma proteins. To examine this, the kinetics of uptake from purified human albumin and alpha(2)-macroglobulin, and the effects of inhibitors, were measured using human hepatic (HepG2) and mammary epithelial (PMC42) cell lines. At physiological concentrations (3-6 muM), both cell types took up copper from these proteins independently and at rates similar to each other and to those for Cu-dihistidine or Cu-nitrilotriacetate (NTA). Uptakes from alpha(2)-macroglobulin indicated a single saturable system in each cell type, but with different kinetics, and 65-80% inhibition by Ag(I) in HepG2 cells but not PMC42 cells. Uptake kinetics for Cu-albumin were more complex and also differed with cell type (as was the case for Cu-histidine and NTA), and there was little or no inhibition by Ag(I). High Fe(II) concentrations (100-500 microM) inhibited copper uptake from albumin by 20-30% in both cell types and that from alpha(2)-macroglobulin by 0-30%, and there was no inhibition of the latter by Mn(II) or Zn(II). We conclude that the proteins mainly responsible for the plasma-exchangeable copper pool deliver the metal to mammalian cells efficiently and by several different mechanisms. alpha(2)-Macroglobulin delivers it primarily to copper transporter 1 in hepatic cells but not mammary epithelial cells, and additional as-yet-unidentified copper transporters or systems for uptake from these proteins remain to be identified.

Normally Cu(II) entering the blood plasma binds tightly to albumin (Alb) and the macroglobulin, transcuprein. However, little is known about how this copper is then taken up by hepatic cells, which are main recipients. Two determine this, the kinetics of copper uptake from these plasma proteins, and effects of inhibitors, were measured in the human hepatic (HepG2) and mammary epithelial (PMC42) cell lines. At physiological concentrations (1–5 uM) both cell types took up Cu from purified human Alb and alpha‐2‐macroglobulin (a2M) at rates similar to each other and to those for Cu‐di‐histidine (His). Uptakes from a2M but not from Alb or His obeyed Michaelis Menten kinetics, with Kms of 4–6 uM. Uptake from a2M but not the others was markedly inhibited by Ag(I) in HepG2 but not PMC42 cells. Copper uptake was not inhibited by Fe(II), Mn(II), or Zn(II) except at very high concentrations (200–500 uM). We conclude that the two plasma proteins mainly responsible for the plasma exchangeable copper pool deliver copper as efficiently as amino acid complexes to mammalian cells; that a2M delivers it primarily to CTR1 in hepatic but not mammary epithelial cells; and that additional as yet unidentified transporters responsible for copper uptake from these plasma proteins remain to be identified. Supported by PHS Grant No. RO1 HD 46949.

Abstract. Unprotected sunlight exposure is a risk factor for a variety of cutaneous cancers. Topically used dihydroxyacetone (DHA) creates, via Maillard reaction, chemically fixed keratin sunscreen in the stratum corneum with significant protection against UVA/Soret radiation. When used in conjunction with naphthoquinones a naphthoquinone-modified DHA Maillard reaction is produced that provides protection across the UVB/UVA/Soret spectra lasting up to 1 week, resisting sweating and contact removal. The aim of this study was to examine a simplified version of this formulation for effect on UV transmission and to determine if penetration levels merit toxicity concerns. Permeability was demonstrated for freshly prepared DHA (30 mg/mL) and lawsone (0.035 mg/mL) alone and in combination using a side-by-side diffusion apparatus at 37°C over 48 h across shed snake skin and dermatomed pig skin. These samples were then examined for effectiveness and safety. Concentrations were determined by HPLC and UPLC monitored from 250-500 nm. Lawsone flux significantly decreased across pig skin (20.8 (±4.8) and 0.09 (±0.1)mg/cm 2 h without and with DHA, respectively) but did not change across shed snake skin in the presence of DHA. Significantly reduced lawsone concentration was noted in donor chambers of combined solutions. Damage was not observed in any skins. Darker coloration with greater UV absorbance was observed in skins exposed to the combined solution versus individual solutions. This study confirmed that combined DHA and lawsone provided effective blocking of ultraviolet light through products bound in keratinized tissue. DHA permeation levels in pig skin suggest further in vitro and in vivo study is required to determine the safety of this system.