Discovery of a midgut peptide hormone which activates the endocrine cascade leading to oögenesis in Phormia regina (Meigen)

A midgut hormone was discovered in liver-fed, Phormia regina adult females. Results indicated that this hormone is released from the midgut to reach its target, the brain, between 4–8 h after the onset of the liver meal. The stimulated brain neurosecretory cells then initiate the neuroendocrine cascade leading to the beginning and the completion of oogenesis. A bioassay was developed to measure the midgut hormone activity. High activity of this hormone was detected in midgut extract prepared from midguts of liver-fed females 6 h after the onset of the liver meal. The midgut hormone is partially heat resistant and is not denatured in 80% methanol. Its Mr was estimated to reside between 5000 and 11,000. The true Mr remains to be determined. This is the first hormone identified from insect midgut that connects nutrition and the neuroendocrine system with oogenesis. A working hypothesis concerning the dietary initiated endocrine regulation of oogenesis was proposed for P. regina.