Surveying the Response of Transport Channels of Intact RBC Membranes upon AgNO₃ Administration: an Atomic Force Microscopy Study

Abstract

Background/Aims: Cell membranes facilitate the transport of water, ions, and necessary nutrients by hosting a great variety of transport channels that have either a ‘simple’ pore-like structure or more complex architecture that is based on the utilization of specific receptors. The present study reveals the impact of AgNO₃, a well-known inhibitor of water channel activity, on transport channels that emerge at the membrane of intact red blood cells (iRBCs). Methods: Atomic force microscopy is employed to survey the morphological modification of all transport channels by directly comparing the respective images obtained on the exact same iRBCs prior to and after spraying the AgNO₃ solution. Results: Small pores of mean size 50 nm that were assigned to water channels, and extended orifices of mean size 300 nm that exhibit a neck-like extracellular segment were observed at the iRBC membrane. Conclusion: Our results reveal that AgNO₃ exerts noticeable influence on all transport channels so that its selective water channel inhibitory action should be reconsidered. For low AgNO₃ concentrations extended recovery of the small pore network was observed upon waiting, giving strong evidence that iRBCs have a recovery potential upon simply removing the inhibition cause without the need for specific reducing agents.

Does the extracorporeal circulation worsen anemia in hemodialysis patients? Investigation with advanced microscopes of red blood cells drawn at the beginning and end of dialysis

“…Three-dimensional renderings of the whole cell (pre-HD [ Figure 1A] and post-HD [ Figure 1E]) and most important two-dimensional presentations of specific subareas of the RBC membranes (pre-HD [ Figure 1B show that the RBC membrane exhibits local defects of circular form ( Figure 1A and E), termed "orifices" for the rest of this work. 7,19 These defects were also recorded in the RBCs of the healthy donors. 7,19 An advantage of the AFM technique originates from the fact that obtained information of nanometer resolution comes in digital form.…”

“…7,19 These defects were also recorded in the RBCs of the healthy donors. 7,19 An advantage of the AFM technique originates from the fact that obtained information of nanometer resolution comes in digital form. Thus, it can be processed with the relevant software so that all the desired dimensions of the observed characteristics can be estimated with great accuracy by using the Z profile option (pre-HD [ Figure 1C] and post-HD [ Figure 1G]) of a specific line scan (pre-HD [ Figure 1B] and post-HD [ Figure 1F]).…”

“…7,[17][18][19][20][21][22][23][24][25] With AFM and SEM, we accessed thorough structural information from the membranes of intact RBCs (iRBCs) of HD patients, drawn both pre-and post-HD. A comparison to healthy donors was also performed.…”

“…Finally, we stress that, in this study, the RBCs were subjected to the minimum possible processing to preserve the native landscape of their membrane. In a recent AFM-based study, 19 Stamopoulos et al demonstrated that the biochemically "inert" media that are routinely used in laboratory practice (saline, phosphate-buffered saline, etc) interact with blood cells, modifying the morphological information of the membrane, at least at the nanometer level. The same cautions were raised in a recent SEM-based study on RBCs, 24 in which air-dried smears and paraffinembedded sections were compared.…”

“…Blood samples were subjected to the minimum possible processing, since Stamopoulos et al, in a recent study, 19 showed that media considered to be perfectly inert (such as saline, phosphatebuffered saline, etc) influence blood cells, modifying the original morphological information of their membrane, at least at the nanometer level. Thus, in this study, we focused on iRBCs, that is, RBCs in whole plasma, by keeping additional processing to a minimum.…”