We studied the association between metabolic parameters of urine and blood in relationship with physical and chemical state of cell membranes in patients with urolithiasis.
Materials and Methods: thirty five patients (19 men and 16 women) aged between 23 and 61 years with urolithiasis were evaluated. Microviscosity of cell membranes in patients with urolithiasis and healthy subjects was assessed by fluorescent membrane probes using pyrene as a hydrophobic probe. Level of primary (diene conjugates) and secondary (malondialdehyde) products of lipid per oxidation in blood serum and urine was determined.
Results. Acellular urine supernatant in urolithiasis patients had lipid concentration (15,17 ± 4,70 mg per mmol of creatinine) which surpassed normal values (0,89 ± 0,16 mg per mmol of creatinine) 17 times, which reflected the destruction of membranes ofrenal epithelial cellsin urolithiasis. An increased excretion of primary products of lipid peroxidation (diene conjugates)wasfound. Presence ofsecondary products of lipid peroxidation, which was assessed by concentration of malondialdehyde, in blood plasma and erythrocyte membranesin patientswith urolithiasiswas 1.6 times higher when compared with healthy subjects (p < 0.05), which hinted at oxidative stress in urolithiasis.
Discussion. It is known that intensification of lipid peroxidation in biological membrane leads to an increase in microviscosity due to breaks in chains of polyunsaturated fatty acids in membrane phospholidis. Using pyrene as a fluorescent probe able to introduce itself into hydrophobic inner part of lipid double layer of biomembranes, we demonstrated an increase in microviscosity of cell membranes of blood lymphocytes in patients with urolithiasiswhichwasseemingly related to a systemic activation of lipid peroxidation.The same process of free radical oxidation obviously leadsto a decrease in functional activity of white blood cells stimulated by barium sulphate microcrystals. Amplitude of luminescence flash, which reflects the phagocytic activity of these cells, was 3.6 times lower in urolithiasis patients when compared to healthy subjects (p < 0,001). This reflects and important role of state of plasma membranes in pathogenesis of urolithiasis.
Conclusion: thus, multiple membrane disorders of blood cells(erythrocytes, lymphocytes, granulocytes) and cells ofrenal tubular epithelium are observed in urolithiasis, and this may be interpreted as a manifestation ofsystemic membrane disorderin patientswith oxidative stress.It may be suggested, thatsystemic activation of free radical oxidation, accompanied by an impairment of functionalstate of cell membranes, is one of the most important components in pathogenesis of urolithiasis.
Authors declare lack of the possible conflicts of interests