Failure to detect radioimmunoassayable arginine vasotocin in mammalian pineals

The presence of arginine vasopressin (AVP) and arginine vasotocin (AVT) in pineal and neural lobes of a variety of species was evaluated by radioimmunoassay using two antisera. One antiserum recognizes only AVP, while the other cross-reacts 100% with both AVP and AVT. Only traces of AVP were detected in toad and chicken pituitaries and chicken pineals, tissues found to contain abundant AVT. On the other hand, pineals from rats and rabbits, while containing measurable quantities of AVP, did not contain detectable levels (less than 6 pg) of AVT. These results fail to demonstrate the presence of AVT in rat and rabbit pineals and strongly question the role of AVT as a physiological pineal hormone in mammals.