TY - JOUR T1 - In Vivo and In Vitro Evidence of Blood-Brain Barrier Transport of a Novel Cationic Arginine-Vasopressin Fragment 4-9 Analog JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 561 LP - 568 VL - 290 IS - 2 AU - Shuichi Tanabe AU - Yasuyuki Shimohigashi AU - Yasuhisa Nakayama AU - Takashi Makino AU - Tsugumi Fujita AU - Takeru Nose AU - Gozoh Tsujimoto AU - Teruo Yokokura AU - Mikihiko Naito AU - Takashi Tsuruo AU - Tetsuya Terasaki Y1 - 1999/08/01 UR - http://jpet.aspetjournals.org/content/290/2/561.abstract N2 - The blood-brain barrier (BBB) transport and metabolism of a novel arginine-vasopressin fragment 4-9 [AVP4-9, isoelectric point; (pI) = 9.2] analog, that is, cationic AVP4-9 (C-AVP4-9, PI = 9.8), were examined in vivo and in vitro. At 45 min after an i.v. administration to mice, the cerebrum-to-plasma concentration ratios of 35S-labeled AVP4-9 and 125I-labeled C-AVP4-9were 0.103 and 0.330 ml/g cerebrum, respectively, and the BBB permeation clearances were 1.47 × 10−4 and 3.10 × 10−4 ml/min/g cerebrum, respectively. In the in vitro study using mouse brain capillary endothelial cells immortalized by SV40 infection (MBEC4), the acid-resistant binding values of35S-labeled AVP4-9 and 125I-labeled C-AVP4-9 to MBEC4 at 120 min were 0.93 and 1.95 μl/mg protein (as the cell/medium ratios), respectively.35S-labeled AVP4-9 showed two-phase saturable acid-resistant binding, and its half-saturation constants (KD) were 3.8 nM (high affinity) and 45.7 μM (low affinity). 125I-labeled C-AVP4-9showed single-phase saturable acid-resistant binding, with aKD value of 16.4 μM. The acid-resistant binding of 125I-labeled C-AVP4-9 was significantly dependent on temperature and medium osmolarity. The acid-resistant binding of 125I-labeled C-AVP4-9was inhibited by dancylcadaverine, phenylarsine oxide (endocytosis inhibitors), 2,4-dinitrophenol (a metabolic inhibitor), and AVP4-9, poly(l-lysine), and protamine (cationic substances), but not by poly(l-glutamic acid) (an anionic peptide) and the V1 and V2vasopressin receptor antagonists. In addition, the conversion of C-AVP4-9 to AVP4-9 in the cerebral homogenate was confirmed by HPLC and mass spectrometry. The present results demonstrate that C-AVP4-9 is transported through the BBB more effectively than AVP4-9, via absorptive-mediated endocytosis, and that C-AVP4-9 is converted to the neuroactive parent peptide, AVP4-9, in the cerebrum. The American Society for Pharmacology and Experimental Therapeutics ER -