[Alteration of Ca2+ mobilization and increased circular muscle contractility in colon of stressed rats].
OBJECTIVE
To investigate relationship between the cold-restraint stress induced colonic circular muscle contractility disorder and calcium-handling properties alteration of the affected muscle in rats.


METHODS
Stress was conducted on rats to induce the fecal pellet output increased. Contractile responses to acetylcholine (Ach), KCl, and NaF were determined for colonic circular muscle. To investigate Ca(2+) mobilization, effects of Ca(2+)-free solution, high concentration of extracellular Ca(2+), and pinaverium bromide on the contractility of colon were determined. Prepared sarcoplasmic reticular (SR) of colonic muscle by differential centrifugation and measured Ca(2+)-ATPase activity with colorimetric assay.


RESULTS
In stressed rats, contractile responses of colonic circular muscle to Ach, KCl, and NaF increased significantly; the contraction was more sensitive to high concentration of extracellular Ca(2+) than control. In Ca(2+)-free solution, contractions were significantly suppressed in both groups. Pinaverium dose-dependently blocked contractions acting with different sensitivity on the two preparations. The Ca(2+)-ATPase activity of the SR in stress was lower than control.


CONCLUSIONS
Cold- restraint stress caused a marked increase in the contractility of the colonic circular muscle in rats. Stressed rats' colonic muscle shows an alteration in the homeostasis of intracellular Ca(2+), with appears to be the consequence of increased influx of extracellular Ca(2+), decreased release of intracellular stores of Ca(2+) and a decreased Ca(2+)-ATPase activity of the SR.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003106:Colon / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000503:physiopathology*
D011189:Potassium Chloride; D000252:Calcium-Transporting ATPases; D002118:Calcium