| pubmed-article:7971178 | pubmed:abstractText | Subepithelial fibroblasts of rat duodenal villi were cultured and the physiological characteristics were studied using fura-2 fluorescence. The intracellular calcium concentration (Ca2+i) responded to various substances, i.e., endothelins (ET1 and ET3), substance P, serotonin, angiotensin II, ATP, and bradykinin. The Ca2+i responses to ET1 (> 0.1 nM) and ET3 (> 1 nM) were transient and sometimes followed oscillations that consisted of an initial Ca2+ release from the intracellular store and a sustained Ca2+ influx. Simultaneously with Ca2+i measurement, changes in the cell shape were monitored using fluorescence intensity upon 360-nm excitation. Stellate cells (with thick cell body and slender processes), formed as a result of 1 mM dibutyryl(Bt2)-cAMP treatment, began to change immediately after the short-term application of the endothelin and became flat about 20 min later. This process was not affected by the depletion of extracellular Ca2+ or by the treatment with BAPTA acetoxymethyl ester that completely suppressed the Ca2+i response. Substance P (> 100 nM) increased Ca2+i, but did not induce any morphological changes. The conversion of the shape from flat to stellate, induced by Bt2cAMP treatment, was not accompanied by any Ca2+i change. BQ-123, a specific blocker of the ETA-type receptor, did not block either Ca2+i change or shape conversion at low (100 nM) concentration. The results indicated that shape conversion in subepithelial fibroblasts did not require any Ca2+i response. Our findings regarding the characteristics of subepithelial fibroblasts in intestinal villi imply a functional similarity to astrocytes in the brain. | lld:pubmed |
