Different effects of bile and sodium taurocholate on mucosal calcium accumulation and calcium absorption in rats

To demonstrate different effects of bile and Na taurocholate on calcium absorption, in vivo studies and in situ intestinal loop experiments were performed in intact rats. Only bile (collected from donor rats), but not 15 mM Na taurocholate, significantly increased the jejunal mucosa calcium and 45Ca contents after an intragastric administration of test solution containing 7.5 mM CaCl2 + 45Ca. However, plasma radioactivity which represented lumen to plasma calcium transport was increased by Na taurocholate but not bile, suggesting that both agents enhanced calcium transport across the brush border membrane but in the presence of bile some calcium remained in the mucosal cells. Results from the in situ studies supported the above findings. It was shown that bile and Na taurocholate enhanced the calcium transport from the lumen. However, net absorption was unchanged due to concurrent increase in the efflux of calcium.