DIFFERENTIAL NEUROPHYSIN IMMUNOREACTIVITIES IN SOLITARY MAGNOCELLULARNEURONS OF THE HOMOZYGOUS BRATTLEBORO RAT INDICATE AN ALTERED NEUROPHYSIN MOIETY

In the homozygous Brattleboro rat (di/di) a single base deletion in th e vasopressin (VP) gene causes diabetes insipidus, resulting in the sy nthesis of a VP precursor with a different C-terminus. We reported pre viously that a small number of post-mitotic VP neurons in di/di rats u ndergo a switch to a heterozygous phenotype, suggesting the existence of VP mRNAs with a restored reading frame coding for a normal VP precu rsor. In the present study we report that the increase in the number o f these revertant cells declines after 79 weeks of age. Furthermore, w e provide evidence that the neurophysin (NP) moiety in solitary neuron s is different from normal NP. Comparing the immunoreactivities of two different NP antibodies we deduced that the restoration of the readin g frame may take place downstream of the deletion between amino acids 75 and 93 of the VP-NP.