Inhibitory actions of polysaccharide sulfate on action potentials and contraction of papillary muscles in guinea pigs
Abstract
AIM:
To examine the effects of polysaccharide sulfate (PSS) on the action potentials and contractile force in guinea pig papillary muscles.
METHODS:
Using intracellular microelectrode to record fast (FAP) and slow (SAP) action potentials.
RESULTS:
PSS (> or = 50 mg.L-1) caused concentration-dependent decreases in the contractile force and the action potential duration (APD) of FAP without affecting the resting potential (RP), action potential amplitude (APA), and maximal upstroke velocity (Vmax). The Vmax, APA, and APD of BaCl2-induced SAP were concentration-dependently decreased by PSS (> or = 15 mg.L-1) and the effects were antagonized by isoprenaline (1 mumol.L-1). The APA and APD of isoprenaline-induced SAP were decreased by PSS (> or = 15 mg.L-1) in a concentration-dependent manner and the effects were attenuated by elevation of extracellular Ca2+ concentration.
CONCLUSION:
PSS selectively inhibited the slow inward current.
Keywords:
To examine the effects of polysaccharide sulfate (PSS) on the action potentials and contractile force in guinea pig papillary muscles.
METHODS:
Using intracellular microelectrode to record fast (FAP) and slow (SAP) action potentials.
RESULTS:
PSS (> or = 50 mg.L-1) caused concentration-dependent decreases in the contractile force and the action potential duration (APD) of FAP without affecting the resting potential (RP), action potential amplitude (APA), and maximal upstroke velocity (Vmax). The Vmax, APA, and APD of BaCl2-induced SAP were concentration-dependently decreased by PSS (> or = 15 mg.L-1) and the effects were antagonized by isoprenaline (1 mumol.L-1). The APA and APD of isoprenaline-induced SAP were decreased by PSS (> or = 15 mg.L-1) in a concentration-dependent manner and the effects were attenuated by elevation of extracellular Ca2+ concentration.
CONCLUSION:
PSS selectively inhibited the slow inward current.