In vitro and in vivo effects of erythrocyte phototherapy on newborns.

The photodynamic action of the bilirubin is associated with severe consequences observed during 'in vitro' irradiation of the erythrocytes. This paper is designed to evaluate the bilirubin photodynamic effects which occur 'in vitro' and 'in vivo' on erythrocytes in healthy and jaundiced infants. The in vitro bilirubin sensitized photoreaction damages the erythrocytes mainly at the membrane level. In particular, a dramatic decrease of ATPase activity and an increased susceptibility to lipid peroxidation, expressed as malondialdehyde production, were observed. For in vivo studies, specific fluorescent probes have been used to verify probable changes on the functional architecture of the erythrocyte membrane in the phototherapy-treated infants. Our results showed that specific areas of the membrane are differently affected, mainly at lipid/protein interface. Although the role of the erythrocyte membrane is an important factor of the hemorheological behavior, the measurement of blood viscosity and erythrocyte aggregation and filtration did not show significant alterations during the overall time of phototherapy.