endothelin-1 and 9-anthroic-acid

The effects of 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), anthracene-9-carboxylate (9-AC) (chloride channel blockers) and zaprinast (an inhibitor of phosphodiesterase-5) on endothelin-1 (ET-1) induced contractions of pregnant rat myometrium were investigated in vitro.. Isolated myometrial strips were obtained from pregnant rats, and the strips were mounted in organ baths for recording of isometric tension (n=8). The effects of 10(-7) to 10(-4)M NPPB, 10(-7) to 10(-4)M 9-AC, and 10(-7) to 10(-4)M zaprinast on 10(-8)M ET-1-induced contractions of pregnant rat myometrial smooth muscle were recorded.. NPPB and 9-AC increased the amplitude of ET-1-induced myometrial contractions, while decreasing the frequency, in a concentration-dependent manner. The amplitude of myometrial contractions were significantly increased by NPPB and 9-AC beginning from the concentration of 10(-6)M. The frequency of myometrial contractions were significantly decreased by NPPB and 9-AC beginning from the concentration of 10(-6)M. Zaprinast inhibited the amplitude and frequency of ET-1-induced myometrial contractions in a concentration-dependent manner. Zaprinast-induced decreases in amplitude and frequency of myometrial contractions reached statistical significance beginning from the concentrations of 10(-7)M and 10(-5)M, respectively.. These data provide evidence that the ET-1-induced contractions of pregnant rat myometrial strips may be modulated by chloride channels. In addition, zaprinast effectively inhibited ET-1-induced contractions in pregnant rat myometrium.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Anthracenes; Calcium; Chloride Channels; Cyclic Nucleotide Phosphodiesterases, Type 5; Endothelin-1; Female; Myometrium; Nitrobenzoates; Phosphodiesterase Inhibitors; Phosphoric Diester Hydrolases; Pregnancy; Purinones; Rats; Rats, Wistar; Uterine Contraction

To characterize the effects of endothelin (ET)-1 on the Ca2+-activated Cl- conductance of choroidal arteriolar smooth muscle.. Microvascular smooth muscle cells were enzymatically isolated from choroidal arterioles from the eyes of freshly killed rabbits. Cells were voltage-clamped at -60 mV using the whole-cell perforated patch-clamp technique. Internal pipette solutions were K+ based and contained amphotericin B (200 microg/ml). The cells were bathed in a 20 mM tetraethyl-ammonium solution to block outward K+ currents.. Within 2 to 5 seconds of adding ET-1 (10 nM), inward current pulses were generated at a frequency of around 1 Hz. These evoked transient inward currents were blocked by niflumic acid (10 microM) or anthracene-9-carboxylic acid (1 mM). They were increased 2.4+/-0.1-fold when Cl- was replaced by I in the bathing medium and lost within 4 minutes when external Cl- was reduced from 151.6 to 20 mM. The reversal potential was -1+/-2 mV with 135 mM Cl- in the recording pipette and with 54 mM Cl it was -18+/-4 mV. When gramicidin D (100 microg/ml), which maintains [Cl-]i, was used instead of amphotericin B, the reversal potential was -18+/-1 mV. Ca2+ release by caffeine (10 mM) produced a single transient inward current. Endothelin-evoked transient inward currents were slowly reduced and eventually abolished in Ca2+-free solution (approximately 2 to 3 minutes) and were eliminated after approximately 30 seconds by the sarcoplasmic reticulum Ca2+-uptake inhibitor cyclopiazonic acid (5 microM). The ET(A) receptor antagonist BQ123 (1 microM) prevented an effect by endothelin but did not inhibit the current oscillations once they had been triggered.. In choroidal arteriolar smooth muscle ET-1 evokes transient inward Ca2+-activated Cl- currents induced through the cyclical release and re-uptake of Ca2+ from intracellular stores after ET(A) receptor stimulation.

Topics: Amphotericin B; Animals; Anthracenes; Arterioles; Calcium; Chloride Channels; Chlorides; Choroid; Electrophysiology; Endothelin Receptor Antagonists; Endothelin-1; Female; Gramicidin; Male; Membrane Potentials; Muscle, Smooth, Vascular; Niflumic Acid; Patch-Clamp Techniques; Peptides, Cyclic; Rabbits; Receptor, Endothelin A; Receptors, Endothelin