cardiomyocytes from wild-type and GRK2 knockout (GRK2KO) mice without (sham) or with myocardial infarction (MI). In cardiac myocytes isolated from unstressed wild-type and GRK2KO hearts, myocyte contractions and Ca transients were similar, but GRK2KO myocytes had lower sarcoplasmic reticulum (SR) Ca content because of increased sodium-Ca exchanger activity and inhibited SR Ca ATPase by local pr...

Spontaneous sarcoplasmic reticulum (SR) Ca release causes delayed afterdepolarizations (DADs) via Ca-induced transient inward currents (Iti). However, no quantitative data exists regarding (1) Ca 21 dependence of DADs, (2) Ca required to depolarize the cell to threshold and trigger an action potential (AP), or (3) relative contributions of Ca-activated currents to DADs. To address these points,...

BACKGROUND Ginsenoside Rd (GSRd), one of the most abundant ingredients of Panax ginseng, protects the heart via multiple mechanisms including the inhibition of Ca(2+) influx. We intended to explore the effects of GSRd on L-type Ca(2+) current (I Ca,L) and define the mechanism of the suppression of I Ca,L by GSRd. METHODS Perforated-patch recording and whole-cell voltage clamp techniques were ...

OBJECTIVES The aim of the present study was to assess and compare the dynamics of L-type Ca(2+) current (I(Ca,L)) during physiologic action potential (AP) in canine ventricular cardiomyocytes of epicardial (EPI) and endocardial (ENDO) origin. METHODS I(Ca,L) was recorded on cells derived from the two regions of the heart using both AP voltage clamp and conventional whole cell voltage clamp te...

be induced by stimulus trains for 7.5 seconds only with the BDM or blebbistatin jet (100 nmol/L isoproterenol, 1.0 mmol/L [Ca ]o, 24°C). During sustained arrhythmias, Ca 2 surges preceded synchronous increases in [Ca ]i, whereas the stoppage of the BDM jet made the Ca surges unclear and arrested sustained arrhythmias (n 6). With 200 nmol/L isoproterenol, 2.5 mmol/L [Ca ]o, and the BDM jet, leng...

Transient receptor potential channel (TRPC) genes encode Ca(2+)-permeable channels mediating capacitative Ca(2+) entry (CCE), which maintains intracellular Ca(2+) stores. We compared TRPC gene expression and CCE in human esophageal body (EB) and lower esophageal sphincter (LES), because these smooth muscles have distinct contractile functions that are likely associated with different Ca(2+) reg...

This study was designed to clarify whether simulated microgravity can induce differential changes in the current and protein expression of the L-type Ca(2+) channel (Ca(L)) in cerebral and mesenteric arteries and whether these changes can be prevented by daily short-duration -G(x) exposure. Tail suspension [hindlimb unloading (HU)] for 3 and 28 days was used to simulate short- and medium-term m...

Spontaneous sarcoplasmic reticulum (SR) Ca(2+) release causes delayed afterdepolarizations (DADs) via Ca(2+)-induced transient inward currents (I:(ti)). However, no quantitative data exists regarding (1) Ca(2+) dependence of DADs, (2) Ca(2+) required to depolarize the cell to threshold and trigger an action potential (AP), or (3) relative contributions of Ca(2+)-activated currents to DADs. To a...

The uptake kinetics of waterborne Ca and Cd, both independently and in combination, were examined in C. riparius larvae, which are extremely Cd tolerant. Larvae exposed to Ca (100-2500 micromol L(-1)), exhibited classic Michaelis-Menten saturation kinetics for Ca influx, measured using (45)Ca as a radio-tracer. The maximum rate of Ca influx (J(max)(Ca)) was 0.39 micromol g(-1)h(-1), and the Ca ...

OBJECTIVES Repolarization-prolonging drugs induce torsades de pointes (TdP) in females more than males. The action potential plateau and the early afterdepolarizations that induce TdP are determined, in part, by L-type calcium current (I(Ca,L)). Therefore, we studied gender- and hormone-related differences in I(Ca,L) in age-, and weight-matched normal male, female and hormonally-treated, castra...