Atrial natriuretic peptide augments the blood-brain transfer of water but not leucine and glucose

Recent evidence predicts an effect of atrial natriuretic peptide (ANP) on the blood-brain transfer of water. To test this prediction, we measured the blood-brain transfer of water, l-leucine, and d-glucose in 9 brain regions of male rats after intravenous injection of 10 pmol ANP. The peptide elicited an increase of the permeability-surface area (P_aS) product of labeled water by 28-108% while the P_aS products of leucine and glucose remained unchanged. Cerebral blood flow incresed 15-48% while cardiac output and plasma volume in brain did not alter, indicating no change of capillary surface area (CSA). Regionally, the CSA varied from 63 cm²/g (striatum) to 97 cm²/g (colliculi) and the fraction of capillaries contributing to the total vascular volume varied from 29% (olfactory bulb/lobe) to 62% (striatum). The blood-brain barrier (BBB) permeability to water (5.7 μm/s) was an order of magnitude higher than to glucose (0.4 μm/s) or to leucine (0.3 μm/s).