Development of responsiveness of dispersed rabbit adrenocortical cells to synthetic adrenocorticotropic hormone [ACTH-(1-24)] and alpha melanocyte-stimulating hormone.

Although there is a considerable body of evidence suggesting increased activity of the fetal and neonatal adrenal in the rabbit, the mechanism responsible for this increased activity has not yet been determined. This report provides data on the function of dispersed fetal, neonatal, and adult rabbit adrenocortical cells in vitro. During the period between 22-29 days gestation, the fetal rabbit adrenal cortex increases its cell number and three features of in vitro activity: basal corticoid production, responsiveness to synthetic ACTH-(1-24), and maximum corticoid secretory capacity. None of these variables is significantly altered during the first 3-5 days of neonatal life or in adult rabbits. At no time was any corticoid response observed to alpha MSH.