Age-related changes in cardiac norepinephrine release: role of calcium movement.
The purpose of this study was to determine if the age-related decrease in norepinephrine (NE) release from cardiac adrenergic nerve terminals is due to a defect in Ca2+ movement into the nerve terminal or to an alteration in Ca2+ activation of intracellular events leading to NE release. NE release was assessed in cardiac synaptosomes prepared from 6- and 24-month-old male F344 rats. K(+)-induced NE release was significantly greater in young vs old rats. Raising extracellular [Ca2+] increased NE release, but NE release always remained higher in the younger animals. Ionomycin, a Ca2+ ionophore, induced NE release from cardiac synaptosomes, and there was no age difference in the response. The age-related reduction in NE release induced by K+ and the capacity of ionomycin to induce similar NE release in young and old cardiac synaptosomes points to a reduction in Ca2+ movement during depolarization.
Snyder
D L
DL
Department of Pharmacology, Medical College of Pennsylvania, Philadelphia, USA.
Johnson
M D
MD
Aloyo
V
V
Eskin
B
B
Roberts
J
J
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008978:Mollusk Venoms / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D013574:Synaptosomes / Q000378:metabolism
D008978:Mollusk Venoms; D015759:Ionomycin; D008274:Magnesium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine