ATRIAL-NATRIURETIC-PEPTIDE SECRETION FOLLOWING SUBARACHNOID HEMORRHAGE IN SPONTANEOUSLY HYPERTENSIVE RATS

Atrial natriuretic peptide (ANP) is released excessively in spontaneou sly hypertensive rats (SHR), and vasodepression is its main effect on the blood vessels. The aim of the study was to investigate the changes in ANP secretion in the cerebral vasospasm following subarachnoid hem orrhage (SAH) in SHRs. The SAH was induced by the injection of 100 mu l Of unheparinized, autologous blood into the cerebrospinal fluid (CSF ), via a canule formerly inserted into the cisterna magna (CM). In the sham SAH group the SAH was imitated with 0.9% saline injection. The c oncentrations of ANP in the blood samples obtained in the acute and ch ronic stages of vasospasm were radioimmunoassayed with commercial RIA kits (Peninsula RIK 9103). It was found that both SAH and sham SAH ind uced a significant increase in plasma ANP in the chronic phase of vaso spasm. No such changes were observed in the acute phase. This shows th at the chronic cerebral vasopasm following SAH considerably enhances t he ANP secretion in SHRs, probably through the increased endothelin re lease. These compensatory and regulatory mechanisms help prevent the d evelopment of brain oedema and the progression of vasopasm through sec ondary vasodilation.