Effect of ischemia on sarcolemmal Na+-Ca2+ exchange in neonatal hearts.

Abstract

We studied the effect of cardiac ischemia on sarcolemmal enzymes, Na+-Ca2+ exchange, Ca2+ binding, and Ca2+ efflux in the newborn and adult rabbit. Rabbit ventricle was made ischemic by incubation in hypoxic, glucose-free Tyrode solution at 37 degrees C for 60-120 min. Ischemia inhibited Na+-K+-ATPase and K+-p-nitrophenylphosphatase (PNPPase) activity in the adult myocardium more than in the newborn. In the oxygenated (control) hearts, Na+-Ca2+-exchange activity in the newborn sarcolemma [Michaelis constant (Km) 18 microM; maximum velocity (Vmax) 33] was similar to that in the adult (Km = 16 microM, Vmax = 32). After 60 min ischemia, however, Na+-Ca2+ exchange in the newborn (Km = 16 microM, Vmax = 18) was inhibited less than in the adult (Km = 25 microM, Vmax = 18). In the two age groups, Ca2+ binding and efflux rate were not increased after ischemia, which suggested that Ca2+ permeability did not increase during ischemia. In conclusion, ischemia inhibited sarcolemmal enzymes and Na+-Ca2+ exchange in the newborn less than in the adult, and this lesser inhibition might contribute to or be caused by the greater tolerance of the newborn heart to ischemia.

• Authors: H Meno, J M Jarmakani, K D Philipson
• Journal: The American journal of physiology (Am J Physiol) Vol. 256 Issue 6 Pt 2 Pg. H1615-20 (Jun 1989) ISSN: 0002-9513 [Print] United States
• PMID: 2544110 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Adenosine Triphosphatases
• sodium calcium ATPase
• Sodium-Potassium-Exchanging ATPase
• Calcium

Topics

• Adenosine Triphosphatases (metabolism)
• Aging
• Animals
• Animals, Newborn
• Calcium (metabolism)
• Coronary Disease (enzymology)
• Heart (growth & development)
• Kinetics
• Male
• Myocardium (enzymology)
• Rabbits
• Sarcolemma (enzymology)
• Sodium-Potassium-Exchanging ATPase (metabolism)