Tsai C L, Pu H F, Wang P S, Liu T K
Department of Orthopaedic Surgery, College of Medicine, National Taiwan University, Taipei.
J Gerontol. 1992 Mar;47(2):B45-7. doi: 10.1093/geronj/47.2.b45.
The effects of aging and estradiol on the concentration of plasma calcium in response to human calcitonin (hCT) were investigated in rats. Old (20 months) and young (2 months) female rats were catheterized via the right jugular vein and the left femoral vein before an infusion of 1 nM hCT (0.1 ml/min) into the left femoral vein. Young ovariectomized (Ovx) rats were injected subcutaneously with estradiol benzoate (EB, 25 micrograms/kg) or oil once daily for 3 days before hCT challenge. Blood samples were collected from the jugular catheter before and after the hCT infusion. The basal level of plasma calcium was not affected by age. The infusion of 1 nM hCT decreased the plasma calcium concentration by 18% in old and by 29% in young female rats. The post-infusion levels of plasma calcium were comparatively higher in old rats than in young rats (p less than .05 at 30 min and p less than .02 at 90 min). In young rats, the responses of plasma calcium to hCT infusion were reduced after ovariectomy. Short-term estrogen injection, however, did not restore the sensitivity of young Ovx rats to the CT infusion. These findings suggest that the plasma calcium level in response to calcitonin is decreased in rats during aging. The reduction of the hypocalcemic effect of calcitonin in old female rats at least was estradiol-independent.
研究了衰老和雌二醇对大鼠血浆钙浓度在人降钙素（hCT）作用下的影响。在经左股静脉输注1 nM hCT（0.1 ml/分钟）之前，对20月龄的老年雌性大鼠和2月龄的年轻雌性大鼠经右颈静脉和左股静脉插入导管。在hCT激发前3天，对年轻去卵巢（Ovx）大鼠每天皮下注射一次苯甲酸雌二醇（EB，25微克/千克）或油，共3天。在hCT输注前后，从颈静脉导管采集血样。血浆钙的基础水平不受年龄影响。输注1 nM hCT使老年雌性大鼠的血浆钙浓度降低18%，年轻雌性大鼠降低29%。输注后老年大鼠的血浆钙水平比年轻大鼠相对更高（30分钟时p<0.05，90分钟时p<0.02）。在年轻大鼠中，去卵巢后血浆钙对hCT输注的反应降低。然而，短期雌激素注射并未恢复年轻Ovx大鼠对CT输注的敏感性。这些发现表明，衰老过程中大鼠对降钙素的血浆钙水平降低。老年雌性大鼠降钙素降钙作用的降低至少与雌二醇无关。
