Increased concentrations of immunoreactive cathepsin D in supraoptic nucleus of the Brattleboro rat

The distribution of cathepsin D, an aspartyl endopeptidase, was measured in selected, discrete nuclei of the forebrain of the Brattleboro rat by means of microdissection and radioimmunoassay. The results indicate that cathepsin D is widely distributed, but in varying amounts among nuclear groups in this region of the brain. High concentrations were detected in the supraoptic and paraventricular nuclei. In studies of the vasopressin-deficient Brattleboro rat, an increased content of cathepsin D in the supraoptic nucleus was observed compared to the heterozygous control. No differences were detected between homozygous and heterozygous Brattleboro rats in the caudate, medial preoptic, suprachiasmatic or paraventricular nuclei or globus pallidus. These results raise the possibility that brain cathepsin D may be involved in the physiological events related to fluid homeostasis.