The role of intracellular and extracellular calcium in mechanical and intracellular electrical activity of human urinary bladder smooth muscle.
We studied the role of extracellular and intracellular Ca2+ in human detrusor smooth muscle contraction. Simultaneous recordings of mechanical and intracellular electrical activity were made in three different Ca2+ concentrations: normal Krebs' solution (100%), 10% of the standard Ca2+ concentration and a solution in which Ca2+ was omitted from the medium (0%). Spontaneous contractions and KCl or CCh induced contractions were studied. Ryanodine and caffeine were used to manipulate the intracellular Ca2+ stores. The present results show that only a very small amount of Ca2+ in the extracellular space is sufficient to support spontaneous and induced contractions. Spike-shaped potentials and long lasting depolarisations were recorded in all three solutions. However, the prevalence of long lasting depolarisations increased when the extracellular Ca2+ concentration was reduced. The amplitude of the spike-shaped potentials and long lasting depolarisations appeared to be negatively affected by diminishing the extracellular Ca2+ concentration. Additionally, the duration of the long lasting depolarisations was reduced in 0% Ca2+. The contraction upon KCl stimulation was primarily depending on the extracellular Ca2+. Upon muscarinic receptor stimulation, a combined activation of Ca2+ mobilisation from intracellular and extracellular stores may occur; the ratio of contribution of these two sources changes in accordance with the requirements of the conditions.
Visser
A J
AJ
Department of Urology-Urodynamics, Erasmus University Rotterdam, The Netherlands. visser@udn.fgg.eur.nl
van Mastrigt
R
R
D000109:Acetylcholine / Q000494:pharmacology; D000368:Aged; D000369:Aged, 80 and over; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*
D011189:Potassium Chloride; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium