A cytochemical bioassay method for the determination of luteinizing hormone in biological fluids and tissues.

1 The ability of luteinizing hormone (LH) to alter the reducing activity of corpora lutea in rat ovarian sections has been exploited to develop a new cytochemical bioassay for the hormone. 2 Sections of ovaries, removed from mature rats during the second day of dioestrus, were incubated with either standard LH or samples diluted for assay, stained immediately for reducing potential and the intensity of the stain measured by scanning and integrating microdensitometry. 3 An inverse linear relationship existed between the density of the stain and the logarithm of the concentration of standard LH (68/40) and the dose-response lines of serial dilutions of rat or human plasma were parallel with those of the standard. 4 The method was found to be accurate, specific, sensitive, precise and suitable for the determination of LH in the rat and in man.