Effect of gamma radiation on the transport of spin-labeled compounds across the erythrocyte membrane

Abstract

The effect of ionizing radiation on the non-electrolyte, anion and cation permeability of the erythrocyte membrane was studied by measurement of the reduction rate of appropriate nitroxyl derivatives. Irradiation of bovine erythrocytes in the dose-range of 2-50 krad resulted in a regular dose-dependent increase in the reduction rates of a cation (TEMPO-choline) and a hydrophobic non-electrolyte (TEMPO), and non-regular changes in the reduction rate of a hydrophilic non-electrolyte (TEMPOL). The permeation constant for TEMPO-choline also showed a non-regular response to radiation, similar to the response pattern of other red blood cell parameters. These results also demonstrate that the effects of radiation on the transport of various solutes can be used as a means of distinguishing between different channels of membrane transport.

Effect of thiol reagents and ionizing radiation on the permeability of erythrocyte membrane for spin-labeled non-electrolytes

“…Comparison of appropriate q/2 values indicates that i mM pCMB inhibits the permeation of TEMPOL by about 77%, a value compatible with that obtained for inhibition of water transport in human erythrocytes [13]. Previously we demonstrated [5] that a radiation dose of 20 Gy induced a decrease in the erythrocyte membrane permeability for TEMPOL. In this study we observed that at this dose of gamma radiation the inhibitory effect of pCMB on the TEMPOL transport was only slightly enhanced (data not shown).…”

“…Kinetics of permeation of TEMPOL and TEMPO into erythrocytes, monitored on the basis of decrease in ESR signal intensity due to intracellular reduction of labels [5] is shown in Figs. 1 and 2.…”

“…1 and 2. On the basis of kinetics plots, reduction half-times of the labels (tl/2) were computed as net measures of the transport rate [5].…”

“…Cell preparation, measurements of transport of spin-labeled compounds into the erythrocytes using the ESR technique, and estimation of hemolysis was performed as described previously [5]. Inhibitors of transport of hydrophilic non-electrolytes: mercuric chloride (HgC12), p-chloromercuribenzoic acid (pCMB), N-ethylmaleimide (NEM), and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) were added to cell suspensions to obtain final concentration of 10,100, and 1,000 gM.…”

“…The work of Ross and McConnell [11] opened a new way of transport studies employing spin-labeled compounds. In our previous studies we dealt with the effect of gamma radiation on the transport of spin-labeled compounds across the membrane of bovine [5] and human [6,7] erythrocytes using the spin label technique [11]. This study was aimed at an investigation of mechanism of transport of spin-labeled hydrophobic and hydrophilic non-electrolytes using thiol reagents and ionizing radiation, an agent which also affects the thiol groups of membrane proteins [5].…”