Acute exposure of ceramide enhances cardiac contractile function in isolated ventricular myocytes.
1. The sphingolipid ceramide, a primary building block for all other sphingolipids, is associated with growth arrest, apoptosis, and lipotoxic dysfunction. Interestingly, ceramide may attenuate high glucose-induced myocyte dysfunction, produce Ca2+ influx, and augment smooth muscle contraction. To determine the role of ceramide on cardiac excitation-contraction (E-C) coupling, electrically paced adult rat ventricular myocytes were acutely exposed to a cell-permeable ceramide analog (10 pm-100 microM) and the following indices were determined: peak shortening (PS), time-to-PS, time-to-90% relengthening, and the maximal velocity of shortening and relengthening (+/-dLdt). Intracellular Ca2+ properties were assessed using fura-2AM fluorescent microscopy. 2. Our results revealed a concentration- and time-dependent increase of PS in ventricular myocytes in response to ceramide associated with an increase in +/-dLdt. The maximal increase in PS was approximately 35% from control value and was maintained throughout the first 20 min of ceramide exposure. However, the ceramide-induced increase in PS was not maintained once the exposure time was beyond 20 min. Acute exposure of ceramide significantly enhanced intracellular Ca2+ release, although at a much lower concentration range. The ceramide-induced augmentation of PS was not significantly affected by inhibition of phosphatidylinositol (PI)-3-kinase, protein kinase C (PKC), ceramide-activated protein phosphatase (CAPP), and nitric oxide (NO) synthase. 3. Our data suggest that ceramide acutely augments the contractile function of cardiac myocytes through an alternative mechanism(s) rather than PI-3-kinase, PKC, CAPP, or NO.
Relling
David P
DP
Department of Pharmacology, Physiology, and Therapeutics, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58203, USA.
Hintz
Kadon K
KK
Ren
Jun
J
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002518:Ceramides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D016257:Fura-2; D006352:Heart Ventricles / Q000166:cytology*; D007700:Kinetics; D008297:Male; D018613:Microscopy, Confocal; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002518:Ceramides; D005456:Fluorescent Dyes; D002118:Calcium; D016257:Fura-2