The pressure inside large arteries is typically ~100 mmHg higher than outside of them. This difference, ΔP, drives a flow of plasma, water and advected/swept-along solutes that would otherwise only transport by (much slower) diffusion, across the porous vessel wall. It is natural to ask whether this flow enters the wall across the endothelium solely through inter-endothelial cell (EC) junctions or whether a portion of it goes through the ECs via membrane proteins from the ubiquitous aquaporin (AQP) family. Belkacemi et al. showed a 4-fold protein expressional change of AQP1 in trophoblast cells after treatment with arginine vasopressin (AVP). Using cultured bovine aortic (BA)EC monolayers we have titrated an AVP concentration that shows a marked increase in transmural water flow, Jv, consistent with AQP1 upregulation. Using tracers that only traverse the endothelium via EC junctions, we have shown that AVP does not affect junctional transport. We are now using our titrated AVP values to see if similar Jv upregulation can be obtained in whole rat aortas ex vivo and complement this with studies to directly check upregulation.
Specific Aims: Study AVP-induced differences in BAEC monolayer and whole rat aortic EC AQP1 expression and water filtration properties . (A) Measure/ compare Jv of treated /untreated monolayers and of whole rat aortas ex vivo;(B) Perform solute drag experiment to investigate paracellular transport in treated/ control BAEC monolayers; (C) Quantify AVP-induced AQP1 protein expression change in ECs using immunohistochemistry, Western Blot, Quantitative Real Time Polymerase Chain Reaction (Q-RT-PCR) of AQP1 mRNA.