The presence of atrial natriuretic peptide in canine cerebrospinal fluid and its possible origin in the brain

The presence of atrial natriuretic peptide (ANP) in canine cerebrospinal fluid (CSF) was clearly demonstrated and an attempt was made to determine its origin as either the brain or the atrium. The concentration of ANP in canine CSF was 0.78 +/- 0.37 pmol/l (n = 31) and showed no evident correlation with that in plasma (r = 0.12). Physiological doses of human alpha-ANP (alpha-hANP) were continuously infused intravenously into nine dogs, and ANP concentrations in CSF and plasma were examined six to eight times within a 120-min period following this. The ANP level in CSF was not influenced by the systemic administration of alpha-hANP up to 180 min. Only one low molecular weight peak corresponding to alpha-hANP could be obtained from the CSF samples, while both low and high molecular weight peaks were observed for plasma ANP by gel permeation chromatography. In the atrial and hypothalamic tissue extracts the same kinds of peaks were also evident. These results prove the presence of ANP in canine CSF and that it does not come from blood that has seeped across the blood-CSF barriers, but suggest that it may originate from the brain.