Developmental changes in molecular forms of immunoreactive adrenocorticotropin in the anterior pituitary gland of humans

Abstract

In extracts of anterior pituitary tissue obtained at autopsy of fetal, infant, and adult humans, five molecular forms of immunoreactive ACTH (ACTHi) were detected that had apparent molecular weights of approximately 4044, 30-34, 24-28, 16-18, and 4.5 kilodaltons (K). The relative proportion of each molecular form of ACTHi was similar in tissues that were extracted at the time of autopsy and in tissues that were stored frozen (-20 degrees C) for up to 2 years prior to extraction. We found that 40-44K ACTHi comprised a significantly greater proportion of total ACTHi in fetuses (12.3+/-3.5%) than in adults (3.8+/-0.8%); intermediate amounts of this form of ACTHi (8.0+/-4.1%) were found in tissues obtained from infants. On the other hand, the proportion of 4.5 K ACTHi in fetal pituitaries (67 %) was less than that in those of adults (84 %). The ratio of 40-44/30-34K ACTHi was significantly greater (P<0.001) in fetuses (1.46+/-0.12) and infants (1.31+/-0.07) than in adults (0.52+/-0.07). The ontogenetic differences in molecular forms of pituitary ACTHi are thought to reflect alterations in the processing of proopiomelanocortin as a function of human development.