Fluoxetine competes with cortisol for binding to human serum albumin

Human serum albumin (HSA) is an important protein that carries variety of substances like some hormones and drugs in blood. Pharmacological studies of the interaction of many drugs and HSA are reported during several decades, specially recently years. Interaction of cortisol and fluoxetine hydrochloride (FLX) (as a common anti-stress drug) with HSA (as their carrier in blood) has been studied separately by using different spectroscopic techniques. Here, considering the increment of anti-stress drugs consumption, conformational change of HSA in presence of cortisol and FLX in 50 mM tris buffer, at pH = 7.5 and 37°C, is investigated via pH meter, UV absorption and fluorescence spectroscopy and circular dichroism methods. pH meter findings indicate that the acid denaturation of HSA in the presence of drug and cortisol occurs in the similar manner and this pattern is different relative to the denaturation of HSA in the absence of two reagents. The results of the other techniques consistent with the pH meter findings show that FLX effects on the physiochemical properties of HSA are as that of Cortisol. In-vivo study in Rats confirms in-vitro findings which means blood cortisol level increased in the presence of FLX. Experimental results indicate that FLX and cortisol alter the structural aspects of HSA in similar manner, so, this findings lead to the following reasonable conclusion: "FLX is a competitive ligand for the binding of cortisol to HSA. Binding of FLX to HSA interferes to the interaction of cortisol-HSA."