The effect of parathyroid hormone on the esophageal smooth muscle of the opossum.

The effect of parathyroid hormone on the gastrointestinal motility was studied in vitro. Isolated circular smooth muscle of the opossum esophagus were stimulated by electrical field stimulation in the absence and the presence of increasing concentration of PTH. The addition of 0.1-1.0 U./ml. of PTH to the bath resulted in 21-93% increases in the amplitude of the off response of the circular strips. Complete blockade of the neural transmission with tetrodotoxin abolished the effect of PTH. Atropine (10(-6) M) did not block the augmentatory effect of PTH on the off response. In conclusion, PTH has augmentatory effect on the off response of circulatory smooth muscle of the opossum esophagus. This effect is presumably related to the cryptogenic nerves responsible for the off response. The clinical significance of this effect is yet to be studied.