ATTEMPTS TO ALTER THE CONCENTRATION OF MELANOPHORE HORMONE IN THE PITUITARY GLAND OF THE RAT1

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Abstract
Administration of thyroxine, estrogen, MH (melanophore hormone) and DCA (deoxycorticosteron acetate) to normal rats caused no major deviations in pituitary MH concentration from control values. Surgically blinded rats had normal values, as did those animals exposed to black or white backgrounds. No evidence was produced to indicate a diurnal variation in pituitary MH content. Hydrocortisone and corticotropin administered to the intact rat produced approximately a 40% reduction of the pituitary MH concentration. This depression occurred after 7 days of treatment and appeared to be a maximal effect within the time limits of the experiment. Adrenalectomy caused no appreciable variation from normal values. Both corticotropin and hydrocortisone administered to adrenalectomized rats caused an increased pituitary concentration of MH. These observations do not support the concept of a rapidly adjusting adrenal cortex-MH axis for the rat.