Effects of norepinephrine and isopentenyladenosine on Na+/Ca2+ exchange currents in isolated guinea pig ventricular myocytes.
OBJECTIVE
To study the effects of norepinephrine (NE) and isopentenyladenosine (Iso) on Na+/Ca2+ exchange currents and the receptor mechanism.


METHODS
The quasi-steady state current-voltage relationship from the isolated guinea pig ventricular myocytes was measured using whole-cell voltage-clamp techniques with a ramp pulse protocol.


RESULTS
At potential of +50 mV, NE 0.005, 0.05, and 5 mumol.L-1 increased the Ni(2+)-sensitive current by 29% +/- 9%, 72% +/- 11%, and 124% +/- 31.4%, respectively; Iso 1.5, 150, and 1500 nmol.L-1 caused increases in the Ni(2+)-sensitive current by 2.8% +/- 2.8%, 56% +/- 13%, and 102% +/- 12%, respectively. Propranolol 10 mumol.L-1 completely inhibited the current changes induced by NE and Iso while phentolamine 50 mumol.L-1 showed no effects.


CONCLUSIONS
NE and Iso increased the Na+/Ca2+ exchange currents via stimulation of cardiac beta-adrenoceptor.
Dun
W
W
Department of Physiology, Shanxi Medical University, Taiyuan, China.
Wu
B W
BW
Zhao
R R
RR
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006168:Guinea Pigs; D006352:Heart Ventricles; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D007541:Isopentenyladenosine / Q000494:pharmacology*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011433:Propranolol / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D019831:Sodium-Calcium Exchanger; D007541:Isopentenyladenosine; D012964:Sodium; D011433:Propranolol; D002118:Calcium; D009638:Norepinephrine