Spontaneous dissociation of human pituitary luteinizing hormone in solution

Aliquots of a solution of highly purified human pituitary LH (hLH) were incubated with variations in temperature and time. The incubates were chromatographed on Sephadex G-100 as well as on DEAE-Sephadex A25. The column effluents were assayed in radioligand assay and in specific hLH alpha- and hLH beta-RIA systems. The results indicate that there is spontaneous dissociation of hLH at elevated temperatures under otherwise "normal" conditions concerning, for example, pH and ionic strength. The degree of dissociation is both time and temperature dependent. This dissociation is not due to proteolytic enzymes. It is concluded that one should be alert when using hLH subunit RIA systems at elevated temperatures for measuring hLH levels, e.g. in clinical samples, because artificial high levels may be obtained.