Effects of arginine vasopressin and atriopeptin on glial cell volume measured as 3-MG space

This study evaluates the hypothesis that arginine vasopressin (AVP) and atriopeptin, peptide hormones synthesized and released within the brain, are regulators of brain cell volume using cultured astroglial cells derived from newborn rats. Cell water content, regarded as volume, was measured in defined, serum-free medium as the 3-O-methylglucose (3-MG) space. Initial experiments established conditions such that glucose, which competes with 3-MG for the glucose carrier, would not interfere with the measurement of the 3-MG space. AVP increased the 3-MG space of glial cells by an average of 25% between 30 and 120 min of exposure, whereas atriopeptin decreased it by 32%. The 3-MG space remained close to normal after coadministration of both peptides. The AVP-dependent increase in 3-MG space was blocked both by the V1 antagonist d(CH2)5Tyr(Me)AVP (Manning compound) and by the cotransport inhibitor, bumetanide. Results are consistent with a role for AVP and atriopeptin in the homeostasis of atroglial cell volume.