DIFFERENT ONTOGENESIS OF α-ENDORPHIN POSITIVE CELLS IN THE ANTERIOR AND THE INTERMEDIATE LOBES OF RAT HYPOPHYSIS

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The ontogeny of the rat hypophysis was studied with special reference to the morphogenesis of cells immunoreactive to α-endorphin by the PAP method. The infiltration of mesenchymal cells into the anterior lobe were observed on the 15th day of gestation. On the 16th day, α-endorphin positive cells (corticotrophs) first appeared in the vascular area of the anterior lobe. They were increased in number and intensified in immuno-reactivity up to the 18th day of gestation. It was not until the 17th day of gestation that small patches of α-endorphin positive cells appeared in the intermediate lobe. Nearly all the cells of the intermediate lobe were positive to α-endorphin immediately after birth, as in the adult. The results obtained indicated a difference in morphogenesis of α-endorphin positive cells in the anterior and intermediate lobes.