Neurophysin biosynthesis in normal rats and in rats with hereditary diabetes insipidus.

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Abstract
When [35S]cysteine was injected adjacent to the supraoptic nucleus (SON) in rats, it was rapidly incorporated into proteins in the SON. The [35S]cysteine-labeled proteins extracted from the SON were separated by isoelectric focusing on polyacrylamide gels. Twenty minutes after the injection of [35S]cysteine, 2 major labeled peaks (pI = 5.4 and 6.1) were found in the SON of normal rats; Brattleboro rats had only 1 major labeled peak (pI = 5.4). One hour after the injection, 4 major radioactive peaks were found in the SON of normal animals (pI = 5.1, 5.4, 5.6 and 6.1). Animals with diabetes insipidus had only 2 major labeled proteins (pI = 5.1 and 5.4). Twenty-four hours after normal rats were injected with [35S]-cysteine, all of the labeled peaks described above, except for the one with pI = 5.1, had decreased markedly in size and a small amount of labeled protein with pI about 4.8 was present in the SON. After 24 h the posterior pituitary of normal animals contained 2 [35S]cysteine-labeled proteins with pI = 4.6 and 4.8. The pituitaries of Brattleboro rats had only the pI = 4.6 labeled protein. These pulse-chase data, with data presented elsewhere, indicate that the vasopressin- and oxytocin-neurophysins are synthesized as parts of separate precursors (pI = 6.1 and 5.4, respectively). These precursors are converted into at least 2 intermediates (pI = 5.6 and 5.1) which, in turn, yield the vasopressin-neurophysin (pI = 4.8) and the oxytocin-neurophysin (pI = 4.6).