EMBARGOED UNTIL October 11, 2001
Contact: Donna Krupa: 703.527.7357Cell: 703.967.2751 or [email protected]
Or Onsite APS Registration Desk in CanadaOctober 10-14, 2001Tel.: 1.403.762.6688
VOLATILE ANESTHETICS AND REGULATION OF CARDIAC Na+/Ca2+ EXCHANGE (NCX) IN NEONATES VS. ADULTS
Banff, Alberta, Canada -- When children, especially newborns, are given gas anesthetics for surgical procedures, their hearts slow down and beat more weakly while the anesthetics are being administered. Usually, other drugs need to be given in the operating room to counteract this side effect of anesthetics. A team of researchers has recently examined whether such anesthetic effects on the newborn heart involve one of the mechanisms that regulates calcium in cardiac muscle, which is very important in determining the force with which the heart beats. Newborn hearts are relatively more dependent on a process called sodium (Na+)-calcium (Ca2+) exchange exchange (NCX) for calcium handling during contraction and relaxation, compared to hearts of adults. Every time the heart beats, NCX helps to bring calcium into the cardiac muscle during contraction and helps to push calcium out of the muscle during relaxation. Using an animal model, these investigators determined whether anesthetics interfere more with NCX function in the neonatal heart, and thus cause more cardiac depression during anesthesia.
The findings of the investigation conducted by Y.S. Prakash, Ph.D., L.W. Hunter, Inanc Seckin, and Gary C. Sieck, of the Department of Anesthesiology at the Mayo Clinic, will be presented in detail by Dr. Prakash during the 4th International Conference on sodium-calcium exchange (NCX), Cellular and Molecular Physiology of Sodium-Calcium Exchange. The conference, a gathering of more than 100 international and inter-disciplinary experts, is being sponsored by the American Physiological Society (APS) on October 10-14, 2001 in Banff, Alberta, Canada.
The researchers used rat cardiac cells to examine the theory that anesthetics produce greater cardiac depression in neonates via greater interference with NCX regulation.
Some key results of their study found that:
-- The NCX in neonatal hearts is 50 percent more active (when bringing Ca2+ in or out), compared to adult heart, and may be very important in controlling the force of the heartbeat in neonates.
-- Anesthetics decreased the activity of the NCX by almost 80 percent in neonatal hearts, supporting the theory that interference with this mechanism contributes to the cardiac depression in neonates.
-- Drugs such as isoproterenol (Isuprel(r)) (used in the operating room to help the heart pump harder and push more blood) can increase the activity of NCX, although the neonatal heart is not as responsive to such drugs. Regardless, such drugs appear to partly counteract the inhibitory actions of anesthetics on NCX.
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Editor's Note: Background Information on Sodium-Calcium Exchange
The physiological functions of vision, secretion and cardiac contractility are strongly dependent on sodium-calcium (Na+-Ca2+) exchange activity, according to the proceedings of the last NCX conference held in 1995 and published by the New York Academy of Sciences (Volume 779, p. xiii). Research efforts stem from the realization that "In many cell types, sodium-calcium exchange is the primary mechanism of calcium extrusion, and small changes of sodium-calcium exchange activity have large effects on cell function. In heart and in brain, sodium-calcium exchange activity likely becomes pivotal in pathological settings with possible outcomes of calcium overload, altered electrical activity and ultimately cell death." (p. xiii).
Since the Na+-Ca2+ exchanger (NCX) was first identified in heart muscle in 1968-1969 (p.7), it has been identified in virtually every tissue examined as well as in a variety of species, including human, dog, squid and fruitfly. The 1990 cloning of NCX1 from heart led to the discovery of different NCX isoforms in kidney, brain and vascular smooth muscle, as well as to the cloning of two new NCX genes, NCX2 and NCX3 from mammalian brain and skeletal muscle. A separate sub-family of Na+/Ca2+ exchangers, NCKX, was also identified in eye, brain and smooth muscle, that depend upon and transport potassium (K+) as well as Na+ and Ca2+. These data have provided further avenues for scientific exploration for the benefit of human health.
***To set up an interview with Dr. Prakash, please contact Donna Krupa at 703.527.7357 (direct dial), 703.967.2751 (cell) or [email protected]. Or contact the APS registration desk on-site at 1-403-762-6688.
The American Physiological Society (APS) was founded in 1887to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000members and publishes 3,800 articles in its 14 peer-reviewed journals every year.
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