[An in-vitro study of the sources of intracellular calcium in Ach-induced contractions and electrical depolarization and of the capacity of calcium antagonists to influence them in the canine detrusor]. / Estudio "in vitro" de las fuentes del calcio intracelular en las contracciones inducidas por Ach y despolarización eléctrica y de la capacidad de los calcionantagonistas para influir sobre éstas, en detrusor canino.

An "in vitro" experimental line was designed to study the dependence of the canine detrussor's contractile activity on extracellular calcium, or whether on the contrary there are intracellular sources of this element. If dependence from extracellular calcium could be demonstrated, the capacity of calcium channel blockers to block the input the this ion would be studied. The conclusions arrived at were: 1. Ach- and KCl-induced activity is dependent from extracellular calcium. 2. This activity is also sensitive to the action of calcium channel blockers. 3. Calcium channel blockers block Ach-activated calcium channels completely, but only partially dose activated by KCl. 4. While the activity induced by Ach and resistant to action from calcium channel blockers is probably due to calcium released from the intracellular reservoirs, the activity induced by KCl and resistant to the calcium channel blockers action can be better explained by the activation of the transmembrane channels which cannot be blocked by this agents.

[The ability of extracellular calcium and calcium channel blockers to modify the spontaneous activity of the detrusor muscle. An in-vitro study]. / Capacidad del calcio extracelular y los farmacos bloqueadores de la entrada de calcio para modificar la actividad espontaneo del musculo detrusor. Estudio "in vitro".

The ultimate mechanism of action for all substances with the ability of modifying the activity of smooth muscle is an increased or decreased intracellular concentration of Ca2+. This report presents an "in vitro" study where the dependency on extracellular Ca2+ for the spontaneous activity of the detrusor muscle was investigated, and also the changes that calcium channel blockers can exert on it. The study concludes that the tonic component of the spontaneous activity depends on the Ca2+ intracellular deposits while the physical activity depends on Ca2+ entry from extracellular space. This entry of Ca2+ from the outside is not inhibited by the action of Ca2+ channel blocking agents.