ATRIAL NATRIURETIC PEPTIDE-LIKE (ANP-LIR) AND ANP PROHORMONE IMMUNOREACTIVE ASTROCYTES AND NEURONS OF HUMAN CEREBRAL-CORTEX

Atrial natriuretic peptide (ANP) represents a family of related peptid es originally isolated from cardiac atria that have potent natriuretic , diuretic, and vasorelaxant properties. ANP has previously been local ized in neurons of the rat brain in regions subserving cardiovascular functions and fluid/electrolyte balance and has been localized in astr oglia of the canine brain. To determine whether ANP is present in astr ocytes of the human brain and to validate the canine model for future studies, human brain tissue was obtained from autopsy cases with no br ain damage or neurological or vascular disease. Human brains were obta ined less than 3 h postmortem, and anterior cingulate and striate cort ices were dissected following perfusion or immersion fixation. Immunoh istochemical processing utilized antibodies against the processed form of ANP (ANP IV, ANP(104-128)) and against rat proANP (amino terminus) and the avidin-biotin-peroxidase technique. Isolated, strongly ANP-im munoreactive protoplasmic astrocytes were observed in all layers of th e cingulate and striate cortex gray matter. ANP-positive fibrous astro cytes were observed in the white matter. Additionally, distinctive imm unopositive astrocytes were found both within and immediately subjacen t to the glia limitans. Antibody against the prohormone stained only p rotoplasmic astrocytes and sublimitans astrocytes and processes. In ad dition to the astroglia, ANP was detected in scattered multipolar neur ons in the cerebral gray matter. These results provide additional evid ence for diversity of peptide localization in astrocytes and suggest r oles for ANP in the local regulation of cerebral blood flow, blood-bra in barrier permeability, or cerebrospinal fluid volume. (C) 1994 Wiley -Liss, Inc.