Sarcolemmal hydraulic conductivity of guinea-pig and rat ventricular myocytes

T Ogura
2002 Cardiovascular Research  
Objective: Osmotic gradient-induced volume change and sarcolemmal water permeability of cardiac myocytes were evaluated to characterize the mechanism of water flux across the plasma membranes. Methods: Cell surface dimensions were measured from isolated guinea-pig and rat ventricular myocytes by digital videomicroscopy, and membrane hydraulic conductivity (L ) was obtained by analyzing p the time course of cell swelling and shrinkage in response to osmotic gradients. Results: Superfusion with
more » ... Superfusion with anisosmotic solution (0.5-4 210 times normal osmolality) caused a rapid (,3 min to steady states) and reversible myocyte swelling or shrinkage. L was¯1.9310 l p 21 21 210 21 21 N s for guinea-pig myocytes and¯1.7310 l N s for rat myocytes at 35 8C. Arrhenius activation energy (E ), a measure of a 21 the energy barrier to water flux, was¯3.7 (guinea-pig) and¯3.6 kcal mol (rat) between 11 and 35 8C; these values are equivalent to E a 21 2 1 of self-diffusion of water in bulk solution (¯4 kcal mol ). Treatment with 0.1 mM Hg , a sulfhydryl-oxidizing reagent that blocks membrane water channels, reduced L by¯80%, and the sulfhydryl-reducing reagent dithiothreitol (10 mM) antagonized the inhibitory p 21 31 action of Hg . Inhibition of the volume-sensitive cation (30 mM Gd ) and anion (1 mM 4,49-diisothiocyanostilbene-2,29-disulfonate) 1 1 channels and Na -K pump (10 mM ouabain) modified the size of osmotic swelling but had little effect on L . Conclusions: Although p the observed L is relatively small in magnitude, the low E and the sulfhydryl reagent-induced modification of L are characteristic of p a p channel-mediated water transport. These data suggest that water flux across the sarcolemma of guinea-pig and rat heart cells occurs through parallel pathways, i.e., the majority passing through water channels and the remainder penetrating the lipid bilayers.
doi:10.1016/s0008-6363(02)00267-5 pmid:12031705 fatcat:nakndftthjh3njtkqwbttic3iq