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Research Article

ScienceAsia 18 (1992): 041-051 |doi: 10.2306/scienceasia1513-1874.1992.18.041

 

CALCIUM FLUXES ACROSS IN SITU INTESTINAL LOOPS IN OVARIECTOMIZED RATS

 

N. Krishnamra and L. Limlomwongse

ABSTRACT: This study aimed to evaluate effects of ovariectomy and estradiol replacement on caldum fIuxes across different intestinal segments. Sham-operated and ovariectomized (OV) rats had either in situ duodenal and colonic loops filled with 0.5 mM CaCl2 + 45Ca or jejunal and ileal loops Filled with 2.5 mM CaCl2 + 45Ca. Five to six weeks of ovariectomy was found to induce hypocalcemia which could be prevented by daily injection of 3 g estradiol/100 g rat. In sham rats, both duodenal and colonic loops exhibited net secretion while jejuna1 and ileal loops showed net absorption of calcium. Ovariectomy significantly enhanced the plasma to lumen flux of calcium in duodenal and colonic loops while reducing the lumen to plasma flux of calcium in jejunal and ileal loops. These changes in calcium fluxes were prevented by estradiol administration. From this data, it could be concluded that reduction in passive absorption of calcium in the jejunum and ileum together with enhanced calcium secretion in the duodenum and colon constituted caldum loss from the gastrointestinal tract which may partly account for ovariectomy induced hypocalcemia.

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Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand.

Received January 31, 1992