A slow and a fast secretory compartment of POMC-derived peptides in the neurointermediate lobe of the amphibian Xenopus laevis.

1. Peptide release from the neurointermediate lobe of Xenopus laevis has been studied using dual pulse-chase incubation, superfusion and HPLC techniques. 2. Lobes release pulse-labelled material in two phases, the first phase lasting about 6 hr, the second persisting up to 14 hr. 3. In both phases similar, POMC-derived peptides are released. Their release can be inhibited by dopamine. 4. When release during the first phase is inhibited, newly synthesized peptides are shunted into the second release pathway. 5. It is concluded that the neurointermediate lobe contains two release compartments. The possible locations of these compartments within melanotrope cells have been discussed.