EFFECT OF TEMPERATURE AND PH ON THE MAGNITUDE OF THE FREE FRACTION OFCORTISOL IN SERUM

Concomitant effects of temperature and pH on changes in the magnitude of the free, unbound fraction of cortisol in human serum were studied at temperatures and pH ranging from 36 to 39 degrees C and from 6.9 to 7.4, respectively. Free fraction increased with increasing temperatur e and decreasing pH, the two factors acting synergically: a rise in te mperature from 36 to 39 degrees C caused an about 30% increase in the free fraction at pH = 7.4, and at pH 6.9 - over 2.2-fold. At highest t emperature-acidity combination, i.e. at 39 degrees C, pH = 6.9, the fr ee fraction was as much as 2.5-fold higher, relative to standard condi tions (pH 7.4, 37 degrees C). This implies that in vivo the free, biol ogically active fraction of cortisol may increase due to e.g. hyperthe rmia and acidosis at a constant total concentration of this hormone.