Dependência térmica dos efeitos de glicerol e sorbitol a 1 M sobre a estabilização e desestabilização in vitro de eritrócitos humanos por etanol

Abstract

CAPÍTULO II:Incubation of erythrocytes in saline solutions with increasing concentrations of ethanol produces morphological and physicochemical alterations. In saline solution of 2% ethanol, erythrocytes are present in an expanded morphological state (R) and are designated as echinocytes. Between 12.52 and 16.10% ethanol in saline solution, the R state erythrocytes suffer a sigmoidal lysis transition, with a half-transition point (D50R) at 14.28% ethanol. But between 24.67 and 28.37%, erythrocytes present a stabilization transition with a half-transition point (S50) at 26.49% ethanol. In saline solution of 32% ethanol, integer erythrocytes are present, among lysed cells, in a contracted morphological state (T) and are designated as espherocytes. At 28.37% ethanol begins a sigmoidal lysis transition of the T state of the erythrocytes, with a half-transition point (D50T) at 34.76% ethanol. The stabilization transition followed but the destabilization transition by ethanol forms a hole or pocket in the lysis curve of erythrocytes by ethanol. The present work had the aim to study the effect of two osmolytes, glycerol and sorbitol, both at 1 mol.L-1, on the thermal dependence of the stabilization and destabilization of erythrocytes by ethanol in physiological saline solution. The stabilization transition was characterized by the half-transition point (S50) and by the deepness of the stabilization sigmoid (PS) of the erythrocytes, which constitutes an estimative of the stabilized population of erythrocytes. The lysis transition of the stabilized state (T) was characterized by the half-transition point (D50T) and by the deepness of the destabilization sigmoid (PD) of the erythrocytes, which constitute an estimative of the lysed population of erythrocytes. The S50 values presented statistically significant linear declines with the temperature increase in pure saline as in saline solution of glycerol and sorbitol; on the other side, the thermal dependence lines of S50 presented lower S50 values in saline solutions of glycerol or sorbitol than in a pure saline solution. This shall mean that the stabilization effect of the erythrocytes has an osmotic origin, since the temperature increase as the incorporation of glycerol or sorbitol to the solution increased the osmotic pressure of the medium. Although the PS values were not significantly changed by the temperature increase, the presence of glycerol and sorbitol produced significant thermal dependences for PS. At the lower temperatures of the interval the presence of glycerol or sorbitol decreased significantly the population of stabilized erythrocytes, but with the temperature increase there is an increase in the population of stabilized erythrocytes. This suggests that the stabilizing effect of ethanol doesn t have exclusively an osmotic origin, but also an action based on a direct interaction with the lipid bilayer of the membrane. The D50T values presented a negative and statistically significant dependence with the temperature increase in the pure saline solution as well in the saline solution of glycerol or sorbitol. Since the D50T values of the thermal dependencies lines were smaller in the presence of glycerol and sorbitol than they were in the pure saline solution, this indicates that the lysis of the T state of the erythrocytes would have an osmolar origin. The PD values presented positive and significant dependencies in pure saline solution as well as in saline solutions of glycerol and sorbitol. The smaller values of PD observed in saline solutions of glycerol and sorbitol at the lower temperatures of the thermal interval we considered are due to the smaller population of erythrocytes that were stabilized under those conditions. In summary, 1 mol.L-1 glycerol or sorbitol in physiologic saline solution and the temperature increase produce increments in the osmotic pressure of the medium and act in synergism with ethanol in the formation and in the lysis of the T state of the erythrocytes.