Rat kidney Na-K pumps incorporated into low-K+ sheep red blood cell membranes are stimulated by anti-Lp antibody.
A genetic dimorphism of sheep red blood cells characterized by differences in the intracellular K+ concentration of mature red blood cells (low-K+ or high-K+ cells) reflects differences in their Na-K pumps and is known to be linked to the ML blood group system. We investigated the relationship of Na-K pumps in red blood cells from sheep of the low-K+ phenotype with an antigen, Lp, that is restricted to low-K+ cells. Anti-Lp antibody stimulates the Na-K pumps in these cells presumably by relieving inhibition of the pumps by Lp. The questions addressed were as follows: is Lp a molecular entity distinct from pumps and, if so, can it interact with pumps of exogenous origin? Rat kidney Na-K pumps were incorporated by fusion of microsomes into either low-K+ or high-K+ sheep red blood cells. The activity of the exogenous kidney pumps was distinguished from that of the endogenous red blood cell pumps by the low sensitivity of rodent pumps to ouabain. Anti-Lp stimulated by > 50% rat kidney pumps incorporated into immature low-K+ sheep cells. This indicates that Lp is a distinct molecular entity free to dissociate from endogenous pumps and inhibit exogenous pumps. Anti-Lp did not stimulate kidney pumps incorporated into mature low-K+ cells but did stimulate kidney pumps following in vitro maturation of microsome fused reticulocytes, probably reflecting restriction of lateral movement of pumps and antigens by the cytoskeleton in mature cells.
Xu
Z C
ZC
Department of Medicine, McGill University, Montreal, Quebec, Canada.
Dunham
P B
PB
Munzer
J S
JS
Silvius
J R
JR
Blostein
R
R
D000818:Animals; D016922:Cellular Senescence; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism / Q000502:physiology; D007518:Isoantibodies / Q000502:physiology*; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008951:MNSs Blood-Group System; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D051381:Rats; D012756:Sheep; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects
D007518:Isoantibodies; D008951:MNSs Blood-Group System; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium