Suppressive effect of calcitonin on intestinal absorption of calcium and phosphorus in sheep. 
This study was carried out to determine the effect of calcitonin on calcium and phosphorus absorption in sheep.  Six sheep, which were prepared with a carotid loop and a portal venous catheter, were used.  Thyroidectomized sheep were injected intramuscularly with porcine calcitonin at feeding time.  Serum calcium concentrations did not change in intact or thyroidectomized sheep after feeding but calcium venoarterial blood differences in thyroidectomized sheep were higher than in intact sheep 8 h after feeding.  Serum calcium concentrations and calcium veno-arterial blood differences were decreased by calcitonin injection into thyroidectomized sheep.  Calcitonin injection also reduced the serum phosphorus concentrations.  Phosphorus veno-arterial blood differences in thyroidectomized sheep were much less than in intact sheep before feeding although the blood differences were not affected by calcitonin injection in thyroidectomized sheep.  The results indicated that calcitonin decreased calcium absorption, which caused a reduction in the serum calcium concentrations, and that calcitonin injection did not affect phosphorus absorption in thyroidectomized sheep.