A calcitonin-like action of prostaglandin E1

Abstract The pharmacological effects of PGE 1 (6 and 9 days, 21,250 μg/kg per day subcutaneously) upon the growth and the bone resorption of mammals were studied using the proximal tibia and upper incisor of immature rats along with lead acetate as a time marker, and upon the serum calcium and inorganic phosphorus levels. The following results were obtained. 1. PGE 1 hardly affected the body weight or the weight of organs of the rats but apparently inhibited the longitudinal growth of proximal tibia in a dose related manner. 2. PGE 1 clearly inhibited not only the longitudinal growth (incisor growth) but also the appositional growth (dentin formation) of incisal dentin. 3. The grade of the inhibitory effect on the growth was in the order of bone growth >dentin formation >incisor growth. 4. The occurrence of osteoporosis due to a low calcium diet was inhibited by the simultaneous administration of PGE 1 , the mechanism being considered to be mainly due to the inhibitory effect on the bone resorption. 5. PGE 1 lowered the level of serum calcium and the lowering effect was not observed in the thyro-parathyroidectomized rat. From the facts that the above effects were exactly the same as those of calcitonin (1), the possibility that the subcutaneous injection of PGE 1 may induce a calcitonin-like action, a part of which may dependent on the calcinonin secretion is suggested.