Abstract
We have investigated the effect of the dihydropyridine calcium channel agonist, Bay K 8644, and of the plant alkaloid blocker of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum, ryanodine, on the refractory period, action potential and mechanical response of the guinea-pig isolated ureter to electrical stimulation. All experiments were performed in ureters pre-exposed to 10 μM capsaicin to eliminate the inhibitory influence exerted by local release of sensory neuropeptides on ureteral excitability and contraction. In organ bath experiments, electrical field stimulation with parameters which produce direct excitation of ureteral smooth muscle (train of pulses at 10 Hz, 5 ms pulse width, 60 V for 1 s) produced tetrodotoxin- (1 μM) resistant phasic contractions. The response to EFS was abolished by nifedipine (1 nM-3 μM) and was enhanced by Bay K 8644 (1 nM-3 μM). In the presence of Bay K 8644 (1 μM), nifedipine (30 μM) abolished the evoked contractions. Ryanodine (10–100 μM) had no significant effect on the amplitude of evoked contraction. The response of the guinea-pig ureter to direct electrical stimulation of smooth muscle is characterized by a refractory period: at least 40 s interstimulus interval was required to produce a second response in all preparations tested. Bay K 8644 (1 μM) markedly reduced the refractory period of the ureter and a similar effect was observed with ryanodine (100 μM). To further analyze the effect of Bay K 8644 and ryanodine on the refractory period, the response of the ureter was investigated over a 10 s period of stimulation (other parameters as above). In control ureters, continuous stimulation for 10 s produced only one phasic contraction just after the beginning of the train of stimuli. In the presence of Bay K 8644 or ryanodine, more than one phasic contraction developed during a 10 s stimulation, i.e. the refractory period became shorter than the train duration. When both Bay K 8644 and ryanodine were tested on the same preparations, an additive excitatory effect was observed on the mechanical response to electrical stimulation. A slight elevation of KCI concentration (5–10 mM) reduced the refractory period of the ureter as observed with ryanodine or Bay K 8644. Application of KCI (80 mM) produced a biphasic contractile response of the ureter: a series of phasic contractions occurred first, which were then replaced by a slowly developing tonic response. Bay K 8644 (1 μM) enhanced both components of the response to KCI. Ryanodine (10 and 100 μM) markedly prolonged the duration of phasic contractions evoked by KCI and, at 100 μM, slightly (about 25%) reduced the amplitude of tonic contraction.
In sucrose gap experiments, electrical stimulation (single pulse, 40–130 V, 1–3 ms pulse duration) evoked an action potential and accompanying phasic contraction which were abolished by 1 μM, nifedipine. Bay K 8644 (1 μM) produced a marked prolongation of action potential duration, increased the number of spikes and enhanced contraction amplitude and duration. Ryanodine (100 μM) depolarized the membrane, reduced the delay between stimulus application and onset of the action potential, shortened the action potential at 50% of repolarization and increased afterhyperpolarization, without producing marked effects on the accompanying mechanical response. KCI (5 mM) likewise produced a slight membrane depolarization and decreased latency between stimulus application and onset of the action potential but did not affect action potential duration. The combined administration of ryanodine and Bay K 8644 produced additive effects on action potential and contractions: furthermore, the contractile phase of the overall contraction-relaxation cycle was significantly prolonged by the combined administration of the two agents, an effect not observed with either drug alone. In the presence of both Bay K 8644 and ryanodine, multiple action potentials and contractions were observed during a train of pulses delivered at a frequency of 1 Hz for 12 s: when a second action potential was triggered before relaxation of the preceding contraction, a summation of the contractile response was observed. These findings demonstrate that availability of voltage-dependent L-type calcium channels is a major mechanism in determining the refractory period of the guinea-pig ureter and, consequently, can be considered as a limiting step in regulating the maximal frequency of ureteral peristalsis. Furthermore, a ryanodine-sensitive mechanism regulates the excitability and contraction-relaxation cycle of ureteral smooth muscle. The increased electrical excitability of the ureter observed in the presence of ryanodine may involve blockade of transient outward currents triggered by spontaneous calcium release from the store and consequent membrane depolarization.
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References
Aickin CC, Brading AF, Burdyga TV (1984) Evidence for sodium-calcium exchange in the guinea-pig ureter. J Physiol (Lond) 347:411–430
Amann R (1993) Neural regulation of ureteric motility. In: Maggi CA (ed) Nervous control of the urogenital system. Harwood, Chur, Switzerland, pp 209–226
Amedee T, Mironneau C, Mironneau J (1987) The calcium channel current of pregnant rat single myometrial cells in short-term primary culture. J Physiol (Lond) 392:253–272
Artemenko DP, Bury VA, Vladimirova IA, Shuba MF (1982) Modification of the single sucrose-gap method. Physiol Zhurn 28:374–380
Benham CD, Bolton TB (1986) Spontaneous transient outward currents in single visceral smooth muscle cells of the rabbit. J Physiol (Lond) 381:385–406
Bolton TB, Lim SP (1989) Properties of calcium stores and transient outward currents in single smooth muscle cells of rabbit intestine. J Physiol (Lond) 409:385–401
Bozler E (1942a) The activity of the pacemaker previous to the discharge of a muscular impulse. Am J Physiol 136:543–552
Bozler E (1942b) The action potentials accompanying conducted responses in visceral smooth muscles. Am J Physiol 136:552–560
Brading AF, Burdyga ThV, Scripnyuk ZD (1983) The effects of papaverine on the electrical and mechanical activity of the guinea-pig ureter. J Physiol (Lond) 334:79–89
Burnstock G, Prosser CL (1960) Conduction in smooth muscles: comparative electrical properties. Am J Physiol 199:553–559
Campbell KP, Knudson CM, Imagawa T, Leung AT, Sutko JL, Kahl SD, Raab CR, Madson L (1987) Identification and characterization of the high affinity [3Hjryanodine receptor of the junctional sarcoplasmic reticulum calcium release channel. J Biol Chem 262: 6460–6463
Cuthbert AW (1965) The relation between response and the interval between stimuli of the isolated guinea-pig ureter. J Physiol (Lond) 180:225–238
Ganitkevich VY, Isenberg GG (1992) Contribution of calcium-induced calcium release to the [Ca2+]i transients in myocytes from the guinea-pig urinary bladder. J Physiol (Lond) 458:119–137
Ganitkevich VY, Shuba MF, Smirnov SV (1987) Calcium-dependent inactivation of potential-dependent calcium inward current in an isolated guinea-pig smooth muscle cell. J Physiol (Lond) 392:431–450
Hess P, Lansman JB, Tsien RW (1984) Different modes of calcium channel gating behaviour favoured by dihydropyridine calcium agonists and antagonists. Nature 311:538–544
Hisayama T, Takayanagi I (1988) Ryanodine: its possible mechanism of action in the caffeine-sensitive calcium store of smooth muscle. Pflügers Arch 412:376–381
Hoyle CHV (1987) A modified single sucrose gap — junction potentials and electrotonic potentials in gastrointestinal smooth muscle. J Pharmacol Methods 18:219–226
Hwang KS, Van Breemen C (1987) Ryanodine modulation of 45Ca efflux and tension in rabbit aortic smooth muscle. Pflügers Arch 408:343–350
Iino M (1990) Calcium release mechanism in smooth muscle. Jpn J Pharmacol 54:345–354
Imaizumi Y, Muraki K, Watanabe M (1989a) Ionic currents in single smooth muscle cells from the ureter of the guinea-pig. J Physiol (Lond) 411:131–159
Imaizumi Y, Muraki K, Takeda M, Watanabe M (1989b) Measurement and simulation of noninactivating calcium current in smooth muscle cells. Am J Physiol 256:C880-C885
Jenden DJ, Fairhurst AS (1969) The pharmacology of ryanodine. Pharmacol Rev 21:1–25
Johnishi J, Sunano S (1978) The role of membrane electrical activities and extracellular calcium in high K-induced contracture of guinea-pig ureter. Japan J Physiol 28:1–16
Kanmura Y, Missiaen L, Raeymaekers L, Casteels R (1988) Ryanodine reduces the amount of calcium in intracellular stores of smooth muscles of the rabbit ear artery. Pflügers Arch 413:153–159
Kuriyama H, Osa T, Toida N (1967) Membrane properties of the smooth muscle of guinea-pig ureter. J Physiol (Lond) 191:225–235
Lai FA, Meissner G (1989) The muscle ryanodine receptor and its intrinsic calcium channel activity. J Bioenerg Biomembr 21:227–245
Lang RJ (1989) Identification of the major membrane currents in freshly dispersed single smooth muscle cells of guinea-pig ureter. J Physiol (Lond) 412:375–395
Maggi CA, Giuliani S (1991) The neurotransmitter role of CGRP in the rat and guinea-pig ureter: effect of a CGRP antagonist and species-related differences in the action of omega conotoxin on CGRP release from primary afferents. Neuroscience 43:261–271
Maggi CA, Giuliani S (1994) Calcitonin gene-related peptide (CGRP) regulates excitability and refractory period of the guinea-pig ureter. J of Urol (in press)
McPherson PS, Campbell KP (1993) The ryanodine receptor/calcium release channel. J Biol Chem 268:13765–13768
Missiaen L, De Smedt H, Droogmans G, Himpens B, Casteels R (1992) Calcium ion homeostasis in smooth muscle. Pharmac Ther 56:191–231
Muraki K, Imaizumi Y, Kojima T, Kawai T, Watanabe M (1990) Effects of tetraethylammonium and 4-aminopyridine on outward currents and excitability in canine tracheal smooth muscle cells. Br J Pharmacol 100:507–515
Rich A, Kenyon JL, Hume JR, Overturf, Horowitz B, Sanders KM (1993) Dihydropyridine-sensitive calcium channels expressed in canine colonic smooth muscle cells. Am J Physiol 264:C745-C754
Shuba MF (1977a) The effect of sodium-free and potassium-free solutions ionic current inhibitors and ouabain on electrophysiological properties of smooth muscle of guinea-pig ureter. J Physiol (Lond) 264:837–851
Shuba MF (1977b) The mechanisms of the excitatory action of catecholamines and histamine on the smooth muscle of guinea-pig ureter. J Physiol (Lond) 264:853–864
Sutko JL, Ito K, Kenyon JL (1985) Ryanodine: a modifier of sarcoplasmic reticulum calcium release in striated muscle. Fep Proc 44:2984–2988
Suzuki M, Muraki K, Imaizumi Y, Watanabe M (1993) Cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum calcium pump, reduces calcium-dependent potassium currents in guinea-pig smooth muscle cells. Br J Pharmacol 107:134–140
Tsien RW (1983) Calcium channel in excitable cell membranes. Annu Rev Physiol 45:341–358
Uyama Y, Imaizumi Y, Watanabe M (1993) Cyclopiazonic acid, an inhibitor of Ca2+-ATPase in sarcoplasmic reticulum, increases excitability in ileal smooth muscle. Br J Pharmacol 110:565–572
Washizu Y (1967) Membrane potential and tension in guinea-pig ureter. J Pharmacol Exp Ther 158:445–450
Weiss RM (1992) Physiology and pharmacology of renal pelvis and ureter. In: Walsh PC, Retik AB, Stamey TA, Vaughan ED (eds) Campbell's urology, Vol I. Saunders, Philadelphia, PA, pp 113–144
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Maggi, C.A., Giuliani, S. & Santicioli, P. Effect of Bay K 8644 and ryanodine on the refractory period, action potential and mechanical response of the guinea-pig ureter to electrical stimulation. Naunyn-Schmiedeberg's Arch Pharmacol 349, 510–522 (1994). https://doi.org/10.1007/BF00169141
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DOI: https://doi.org/10.1007/BF00169141