Increased osmotic fragility of erythrocytes in chronically jaundiced rats after phototherapy

Effects of bilirubin and phototherapy on osmotic fragility and haematoporphyrin-induced photohaemolysis of normal erythrocytes and spherocytes

AIM

To study the effects of phototherapy on erythrocyte haemolysis in vitro and to determine possible differences in sensitivity to phototherapy between normal erythrocytes and spherocytes.

METHODS

Erythrocytes from four normal healthy donors and two donors with hereditary spherocytosis were treated with bilirubin (160 microM) in the presence of human serum albumin in the molecular ratio bilirubin/albumin 0.8. Treated cells were maintained either in the dark or in blue light (450 nm, 8 mW/cm2, 30 min). The experimental light dose was comparable to 2 h of clinical phototherapy. The osmotic fragility of the treated cells was measured by scoring haemolysis in hypo-osmolar solutions (0.10-0.90% NaCl). The sensitivity to photohaemolysis of cells pre-treated with bilirubin (BR) and/or phototherapy was tested by exposing the cell suspensions to haematoporphyrin and UVA radiation. The delayed (18 h) photohaemolysis was measured by spectrophotometry.

RESULTS

Osmotic fragility, expressed as percentage haemolysis, of normal erythrocytes was more than doubled in the presence of BR combined with phototherapy (n = 6, p < 0.05). In contrast, osmotic fragility of spherocytes was unaffected by either treatment (n = 8, p < 0.05). Increased photohaemolysis was seen in spherocytes treated with BR (n = 13, p < 0.05), phototherapy (n = 13, p < 0.05) and a combination of the two agents (n = 13, p < 0.05) compared with spherocytes without BR in the dark (n = 6).

CONCLUSION

Bilirubin may make the plasma membrane of normal erythrocytes more fragile. Newborns with hereditary spherocytosis may be sensitive to phototherapy.

Erythrocytes-the 'house elves' of photodynamic therapy

Photodynamic therapy (PDT) and fluorescence diagnosis (FD) are being developed for a number of clinical applications. Since fluorophores and photosensitising drugs are usually given systemically their effect on blood elements are of significant importance. Photodynamic effects on erythrocytes occur naturally in patients with erythropoietic protoporphyria (EPP). Exposure to small fluences, as obtained by the erythrocytes when they pass capillaries in the skin, leads to transfer of the photosensitiser protoporphyrin IX (PP IX), from EPP erythrocytes to endothelial cells. Thus, the erythrocytes are partly protected while the endothelial cells suffer photodamage. During photodynamic therapy in vivo erythrocytes are regularly photosensitised. This side effect is partly intended but mostly unwanted, and a summary of this topic is given. Furthermore, the effect of UV-A on erythrocytes that is accompanied with the formation of bilirubin is reviewed. Erythrocytes serve as convenient model cells for experimental research. Such use of erythrocytes to screen new photosensitisers may be of limited value. A combination of photohaemolysis and haemoglobin oxygenation may become the basis for an assay for in vitro phototoxicity. Erythrocytes from birds are good model cells for exploration of physiological and molecular mechanisms involved in PDT. A potential mechanism of PDT induced behaviour resembling apoptosis in erythrocytes is provided.PDT for sterilisation of erythrocyte concentrates has a potential for medical use. Photodynamic effects on the erythrocytes themselves should be avoided. This is realised by choosing a virus-selective photosensitiser, low fluences and treatment of the concentrates with agents like dipyridamole and antioxidants. Future aspects of applications of photosensitisation of red blood cells are discussed.

Testicular changes in newborn rats exposed to phototherapy

In this study we investigated the long-term effects of 72-h continuous phototherapy on the reproductive system of newborn rats. The animals' weight, fertilization rates, and number of newborn and histopathological changes in the gonads in a normal group not exposed to phototherapy and in the test animals were compared. At the age of 24 weeks there were no significant differences between the two groups, apart from the histology of the testicles of the male rats who were exposed to the phototherapy. The study group showed a significantly reduced diameter of the seminiferous tubules when compared to the controls (P < 0.001). It can be postulated that phototherapy may cause histological degenerative changes in the structure of the rat's testes, even though there were no changes in fertilization rates. Further studies are necessary to reveal the effects of phototherapy on humans and to determine the effects, if any, on fertility.

Osmotic fragility of erythrocytes in newborn infants treated by phototherapy

In order to determine the in vivo effect of phototherapy on the erythrocytes' osmotic fragility, we have tested 10 preterm infants treated by continuous phototherapy, for jaundice of prematurity. Heparinized blood was obtained daily, starting before the initiation of phototherapy and ending 24 h after stopping the treatment. The osmotic fragility was tested in duplicate immediately, after 1 h incubation at 40 degrees C and after 24 h incubation at 4 degrees C in darkness. The erythrocytes of the preterm infant during and at the end of phototherapy showed a normal osmotic fragility pattern. Comparing the consecutive curves in each infant did not show any population of osmotically differing erythrocytes. Heating or cooling the erythrocytes did not alter these results. It is concluded that phototherapy does not increase the in vivo osmotic fragility of erythrocytes in newborn.