Changes in the surface charge properties of isolated cardiac sarcolemmal vesicles measured by light scattering. II. Characteristics of rabbit preparations.
Numerous studies suggest that cation-sarcolemmal interactions play an essential role in the excitation/contraction/relaxation cycles of cardiac muscle cells. To help elucidate the molecular mechanisms involved in these processes the cation binding characteristics of isolated rabbit cardiac sarcolemmal vesicles were investigated. Cation-membrane interactions were studied by examining the cation-induced aggregation properties of the vesicles. The results obtained were qualitatively very similar to those previously reported for rat and canine cardiac sarcolemmal vesicle preparations (Leonards, K.S. (1988) Biochim. Biophys. Acta 938, 293-309), indicating that all three species have a shared set of basic membrane characteristics. Specifically the results indicate that cations, such as Ca2+, bind to the sarcolemmal surface, and suggest that two (or more) interacting sites are involved in the process. The selectivity series for the cation-induced aggregation of the sarcolemmal vesicles was: La3+ greater than or equal to Cd2+ much greater than Mn2+ greater than Ca2+ greater than Ba2+ = Sr2+ = Mg2+. Protons (H+) could also induce massive vesicle aggregation at pH 5.60-5.75. However, the results obtained also show that the interactions of cations with the rabbit cardiac sarcolemmal membrane surface are quantitatively distinct from those obtained in either rat or canine sarcolemmal vesicle preparations, thereby confirming the species specific nature of cation-sarcolemmal interactions in cardiac cells.
Leonards
K S
KS
Cardiovascular Research Laboratories, UCLA School of Medicine 90024-1760.
Dhers
C
C
D000818:Animals; D002412:Cations / Q000378:metabolism*; D004285:Dogs; D006863:Hydrogen-Ion Concentration; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D009206:Myocardium / Q000648:ultrastructure*; D011522:Protons; D011817:Rabbits; D051381:Rats; D012508:Sarcolemma / Q000648:ultrastructure*; D012542:Scattering, Radiation; D013499:Surface Properties
D002412:Cations; D011522:Protons; D008274:Magnesium