The blood-brain barrier (BBB) transport and metabolism of a novel arginine-vasopressin fragment 4-9 [AVP4-9, isoelectric point; (pl) = 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 1251-labeled C-AVP4-9 were 0.103 and 0.330 ml/g cerebrum, respectively, and the BBB permeation clearances were 1.47 x 10-4 and 3.10 x 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 of 35S-labeled AMP4-9 and 125l-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 (K(D)) were 3.8 nM (high affinity) and 45.7 μM (low affinity). 125l-labeled C- AVP4-9 showed single-phase saturable acid-resistant binding, with a K(D) value of 16.4 μM. The acid-resistant binding of 125l-labeled C-AVP4-9 was significantly dependent on temperature and medium osmolarity. The acid- resistant binding of 1251-labeled C-AVP4-9 was 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 V2 vasopressin 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.
|Number of pages||8|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|Publication status||Published - 1999 Aug 1|
ASJC Scopus subject areas
- Molecular Medicine