Radioactivity accumulates in the posterior pituitary after intravenous injections of [3H]oxytocin (Aroskar, Chan, Stouffer, Schneider, Murti & du Vigneaud, 1964) or tritiated lysine vasopressin ([3H]LVP) (Willumsen & Bie, 1969). These results allow for the possibility that the neurohypophysial hormones may be taken up by the pituitary after the release of endogenous, or the administration of exogenous, oxytocin and vasopressin. The experiments in vitro of Pliška, Thorn & Vilhardt (1971) and Edwards (1971) showed that uptake of radioactivity occurred after incubation of neural lobes with labelled vasopressin but that much of the activity was not associated with hormone. The present communication describes a study on the uptake of [3H]oxytocin by neural lobes of rats incubated in vitro.
Halved neural lobes were incubated in a bicarbonate buffer (McIlwain & Rodnight, 1962) containing [3H]oxytocin (prepared in the Departement de Biologie, Commissariat à l'Energie Atomique, France) and non-radioactive purified oxytocin