QUANTITATIVE STUDIES OF CHICKEN SOMATOTROPHS DURING GROWTH AND DEVELOPMENT BY MORPHOMETRY, IMMUNOCYTOCHEMISTRY, AND FLOW-CYTOMETRY

Changes in the male chicken somatotroph during growth and maturation h ave been examined by morphometric and immunocytochemical (ICC) analysi s of serial sections of the anterior pituitary gland and by flow cytom etry of dispersed anterior pituitary cells. ICC showed that somatotrop hs are confined to the middle and caudal thirds of the anterior pituit ary gland at all ages from 5 to 26 weeks. At a given age somatotrophs are of equal size at all positions along the cephalocaudal axis of the anterior pituitary gland. However, there are age-related changes: fro m 5 to 11 weeks rises occur in both the mean total somatotroph volume per gland (64%) and the mean number of somatotrophs (78%), while the m ean volume of the single somatotroph is unchanged. From 11 to 18 weeks the mean volume of the single somatotroph decreases 41%. From 18 to 2 6 weeks the mean volume of the somatotroph, the mean total somatotroph volume, and the mean number per gland do not change. Flow cytometry s tudies suggested that somatotrophs from adults have less growth hormon e (GH) than somatotrophs from young birds. The increases in total soma totroph volume and number from 5 to 11 weeks are consistent with the r ise in anterior pituitary GH reported previously. Basic quantitative m orphological information about age-related changes in somatotrophs is reported here. When combined with additional facts from future work, t hey may explain the well documented sharp decline in circulating GH fr om 5 to 11 weeks. (C) 1997 Academic Press.