Maturational changes in Na(+)-K+ pump activity in guinea pig airway smooth muscle.
The effect of maturation on the Na(+)-K+ pump of airway smooth muscle (ASM) was studied. Na(+)-K+ pump activity of tracheal smooth muscle from immature (1- to 2-week-old) and mature (10- to 12-week-old) guinea pigs was measured as the ouabain-sensitive component of the resting membrane potential and as ouabain-sensitive 86Rb+ uptake (using 86Rb+ as a marker for K+). Maturation resulted in decreases in both the contribution of the Na(+)-K+ pump of the resting membrane potential and in ouabain-sensitive 86Rb+ uptake. 86Rb+ efflux from tracheal smooth muscle was similar in tissues from immature and mature guinea pigs, suggesting that maturation has no effect on K+ (or at least 86Rb+) permeability. Na+ and K+ contents of tracheal smooth muscle were estimated from the uptakes of 24Na+ and 86Rb+ at equilibrium. Maturation resulted in a decrease in Na+ content but had no effect on K+ content. Since intracellular Na+ is one of the principal determinants of Na(+)-K+ pump activity, these results suggest that maturation results in a decrease in Na(+)-K+ pump activity in ASM, which may be due to a decrease in Na+ content.
Rhoden
K J
KJ
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA. krhoden@jbpierce.com
Souhrada
M
M
Douglas
J S
JS
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D024510:Muscle Development; D009130:Muscle, Smooth / Q000201:enzymology / Q000254:growth & development*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012414:Rubidium Radioisotopes / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D014132:Trachea / Q000201:enzymology / Q000254:growth & development*
D004791:Enzyme Inhibitors; D012414:Rubidium Radioisotopes; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium