[Atrial natriuretic polypeptide in the human and rat spinal cord]

The widespread distribution of atrial natriuretic polypeptide (ANP) immunoreactive material was demonstrated in the human and rat spinal cord, using specific immunogold-silver staining technique and radioimmunoassay. Immunogold-silver staining studies showed that ANP immunoreactive neurons were quite prevalent in the human spinal cord. ANP immunoreactive neurons were largely found in the ventral horn and less in the dorsal and lateral horns. ANP immunoreactive material was absent with anti-ANP serum preabsorbed with ANP. In rats, radioimmunoassay demonstrated that ANP immunoreactive material was present in whole spinal cord. The highest concentration was found in the sacral spinal cord (21.9 +/- 4.48 ng/g tissue), the moderate in the lumbar (3.78 +/- 0.74 ng/g tissue) and the lowest in the cervical and thoracic (0.58 +/- 0.14 and 0.46 +/- 0.21 ng/g tissue, respectively). Gel chromatography and reverse-phase HPLC revealed multiple molecular forms in the rat spinal cord, but the main molecular form was the 28 amino acid rANP. In vivo study showed that ANP was released from the rat spinal cord by depolarizing concentration of potassium.