Tsai C L, Pu H F, Lau C P, Wang P S, Liu T K
Department of Orthopaedic Surgery, School of Medicine, National Taiwan University, Taipei, Republic of China.
Am J Physiol. 1992 May;262(5 Pt 1):E557-60. doi: 10.1152/ajpendo.1992.262.5.E557.
The effects of aging on calcitonin (CT) secretion in female rats were investigated. Old (24 mo) at constant diestrus status and young (2 mo) at diestrus status rats were either ovariectomized (Ovx) or left intact as controls. Ovx rats were injected subcutaneously with estradiol benzoate (25 micrograms/kg body wt) or sesame oil one time per day for 3 days. All rats were infused with CaCl2 (10 mg/ml) at a rate of 2 ml/h for 30 min via a jugular catheter connected to a peristaltic pump. Blood samples (0.5 ml each) were collected at 0, 30, 60, and 120 min. The basal and post-CaCl2 levels of plasma Ca measured with radioimmunoassay were significantly higher (P less than 0.05-0.01) in old than in young female rats. The pre- and post-CaCl2 levels of plasma Ca and CT in young rats were not altered by Ovx or estradiol replacement. In old rats, Ovx caused a higher (P less than 0.01) level in plasma CT at 0 and 30 min after CaCl2 infusion. Both basal and stimulated levels of plasma CT were higher (P less than 0.01) in old Ovx than in young Ovx rats. These results demonstrated that 1) the increase of plasma CT in response to Ca challenge was greater in old than in young female rats, 2) the influence of estradiol and ovarian function on plasma CT concentration increases as a function of age, and 3) estradiol reduced the plasma CT in response to hypercalcemia in old Ovx rats. The sensitivity of the target tissue of young rats may be lower in response to the modulation of estrogen during hypercalcemia without compromising the secretion and hypocalcemic effect of CT in young rats. All suggested an age-related relationship between estrogen and CT secretion in minute-to-minute regulation during Ca infusion in rats.
研究了衰老对雌性大鼠降钙素（CT）分泌的影响。处于持续动情间期状态的老龄（24月龄）和处于动情间期状态的幼龄（2月龄）大鼠，一部分进行卵巢切除（Ovx），另一部分作为完整对照。对卵巢切除的大鼠每天皮下注射一次苯甲酸雌二醇（25微克/千克体重）或芝麻油，持续3天。通过连接蠕动泵的颈静脉导管，以2毫升/小时的速率向所有大鼠输注氯化钙（10毫克/毫升），持续30分钟。在0、30、60和120分钟采集血样（每份0.5毫升）。用放射免疫法测定的老龄雌性大鼠血浆钙的基础水平和氯化钙输注后的水平显著高于幼龄大鼠（P<0.05 - 0.01）。幼龄大鼠血浆钙和CT的氯化钙输注前、后水平不受卵巢切除或雌激素替代的影响。在老龄大鼠中，卵巢切除导致氯化钙输注后0和30分钟时血浆CT水平升高（P<0.01）。老龄卵巢切除大鼠的血浆CT基础水平和刺激后水平均高于幼龄卵巢切除大鼠（P<0.01）。这些结果表明：1）老龄雌性大鼠对钙刺激的血浆CT增加幅度大于幼龄大鼠；2）雌二醇和卵巢功能对血浆CT浓度的影响随年龄增加而增加；3）雌二醇降低了老龄卵巢切除大鼠对高钙血症的血浆CT反应。在高钙血症期间，幼龄大鼠靶组织对雌激素调节的敏感性可能较低，而不影响幼龄大鼠CT的分泌和降钙作用。所有这些都表明，在大鼠氯化钙输注过程中的分钟调节中，雌激素与CT分泌之间存在年龄相关关系。
