Strain differences in pituitary beta-endorphin and ACTH content in inbred mice

The whole pituitary contents of beta-endorphin and ACTH were found to vary widely among 5 inbred strains of mice. beta-endorphin values were 2.5-fold different and ACTH values 1.5-fold. Strains low in beta-endorphin were also low in ACTH. The existence of genetic differences raises the possibility that there exist, or can be developed, strains with extremely low or high levels of these peptides that would aid research directed at elucidating the physiology of opioid peptides.