Ontogenesis of corticotropes and lactotropes in situ in the pituitary gland of the hamster

Summary The development of corticotropes and lactotropes was investigated in the golden Syrian hamster using an anti-porcine ACTH antiserum and a homologous antihamster PRL antiserum. Oval corticotropes were first visible in the ventral region of the pars distalis at 13 days of gestation. By the end of gestation, corticotropes were found throughout the pars distalis and in the pars intermedia. Corticotropes in the pars distalis of postnatal hamsters were either round or irregularly-shaped, often appearing in clusters. Throughout development, corticotropes often appeared to be surrounding other cells. Scarce, very small lactotropes were first observed in the pars distalis of hamsters on the first postnatal day. The number of these cells, which were either round or polyhedral, increased dramatically between 4 and 20 days of postnatal life. These observations indicate that the sequence of appearance of corticotropes and lactotropes in the hamster is similar to that in other species and that lactotropes are confined to the pars distalis of postnatal hamsters.