Efectos contráctiles dependientes del calcio intracelular inducidos por la serotonina en la arteria umbilical humana / Intracellular calcium-dependent contractile effects of serotonin in the human umbilical artery

Antecedentes: Los vasos umbilicales humanos se caracterizan por la ausencia de inervación y por consecuencia, las diferentes sustancias vasoactivas y la respuesta contráctil a través de los iones de calcio son los factores que determinan el flujo sanguíneo al espacio intervelloso en condiciones normales y patológicas, como es el caso de la preeclampsia eclampsia. Objetivo: Aportar información adicional de la respuesta contráctil de la serotonina en relación al calcio intracelular en la arteria umbilical humana. Material y métodos: Se utilizaron vasos umbilicales procedentes de mujeres con embarazo normoevolutivo, los cuales una vez disecados se cortaron en anillos de 5 mm y se montaron en cámara de órgano aislado, utilizando solución de Krebs con y sin calcio, burbujeada con carbógeno y la temperatura controlada. Se evaluó el efecto contráctil inducido por serotonina a diferentes concentraciones molares y se contrastó con verapamil, lantano y ácido ciclopiazónico, cuantificando la respuesta contráctil mediante un polígrafo biopac acoplado a un sistema computacional. Resultados: No se observaron diferencias significativas en la magnitud de la respuesta obtenida en presencia y ausencia de calcio extracelular. Se apreció el efecto contráctil a la serotonina que disminuyó significati vamente como respuesta a la estimulación repetida a la misma; así mismo, se incrementó el tono basal posterior a la adición del calcio al medio de incubación, lo que dependió del tiempo de exposición. También se observó la inhibición parcial del incremento en el tono basal con vera pamil y lantano. Finalmente, el pretratamiento con ácido ciclopiazónico no modificó la respuesta contráctil a la serotonina en un medio sin calcio. Conclusiones: La contracción inducida por serotonina en la arteria umbilical humana, depende principalmente de calcio intracelular y favorece el ingreso capacitativo de este ion, el cual se incrementa gradualmente a través del tiempo. El ingreso capacitativo del calcio secundario al vaciamiento de los depósitos intracelulares de este ion con serotonina se efectúa a través de canales tipo L y no-L, y no parecen ser sensibles al ácido ciclopiazónico.

Background: Absence of innervation is a hallmark of human umbilical vessels. Intervillous space blood flow is regulated by vasoactive substances and calcium dependent contractility, both in normal and pathological conditions such as preeclampsia eclampsia. Objective: To obtain additional information on the intracellular calcium contractile effects of serotonin in human umbilical arteries. Materials and Methods: Umbilical arteries from normal pregnancies were dissected, cut in 5 mm rings and mounted in a temperature controlled isolated organ chamber, using calciumfree Krebs solution. The contractile effects of serotonin, lantane, verapamil and cyclopiazonic acid were evaluated at different concentrations using a computer coupled biopac polygraph. Results: No differences in response were observed in the presence and absence of intracellular calcium. The positive contractile effects observed with serotonin were significantly decreased with repeated stimulation. An increase in the basal tone of the vessel was observed after calcium supplementation was added to the solution. This effect was minimized in the presence of verapamil and lantane. The contractile effects of serotonin in the calcium free solution were not affected by the presence of cyclopiazonic acid. Conclusions: Serotonin contractile effects in the human umbilical artery depend mainly on intracellular calcium levels which favor the gradual entrance of this ion over time. Calcium influx induced by serotonin is possible through L and Non-L channels apparently insensitive to cyclopiozonic acid.

The Effect of Extracellular Calcium on the Contractile Response to Field Stimulation, Bethanechol and ATP in Rabbit Urinary Bladder / 대한비뇨기과학회지

PURPOSE: In a previous study increasing the extracellular clacium concentration enhanced the phasic contractile response to low frequency stimulation(2Hz) to a significantly greater degree than the enhancement of high frequency stimulation(16Hz). To investigate the sensitivity of the detrusor contractile responses to field stimulation, bethanechol and ATP in calcium free buffer, the current study was designed. MATERIALS AND METHODS: Each rabbit bladder strip of 5x10mm in size was incubated for 30 minutes in the Tyrode's solution. Individual strips were utilized to generate the response to field stimulation(2, 8 and 32Hz), bethanechol(1.0-250microM) or ATP(0.25-2mM). Upon completion of the first stimulation in Tyrode's solution, each tissue was washed 3 1.tomes at 15 minute intervals with fresh Tyrodes. At 15 minutes following the last wash, the Tyrode's solution was replaced with solution containing no calcium+1.0mM EGTA and incubated for ditional 5, 15 or 30 minutes. At the end of 5, 15 or 30-min period of tulibration a second round of field stimulation or dose-response curves to bethanechol or ATP were generated. The contractile responses were monitored via an FT03 force transducer and recorded on a Grass 7D polygraph and expressed as the g tension per 100mg of tissue. RESULTS: (1) Progressive decrease in both basal tension and spontaneous contractile activity (2) more rapid decrease in the contractile response to 2 and 8Hz field stimulation than to 32Hz stimulation (3) more rapid decrease in the contractile response to lower concentrations of bethanechol and ATP than to high concentrations (4) greater maximal inhibition of the contractile response to low concentrations of bethanechol and ATP than to high concentrations. CONCLUSIONS: These results indicated that detrusor contractility to a sub-maximal stimulation rather than maximal stimulation is more sensitive to extracellular calcium depletion.