Mayer G P, Hurst J G
Endocrinology. 1978 Apr;102(4):1036-42. doi: 10.1210/endo-102-4-1036.
Parathyroid hormone (PTH) secretion rate was measured in 16 anesthetized calves by using a technique involving radioimmunoassay of parathyroid venous blood which was collected during timed intervals and measured volumetrically. The calves ranged in age from 2-14 weeks. Plasma calcium concentration was altered by infusion of solutions of CaCl2 or disodium ethylenediamine tetracetate (Na2 EDTA) into the jugular vein. When plasma calcium concentrations exceeded 10.5 mg/100 ml, a basal, non-suppressible secretion rate of 0.3 ng/kg/min was maintained despite the induction of hypercalcemia. Slight changes in secretion rate were observed in response to changes of plasma calcium in the range between 9 and 10.5 mg/100 ml. Below 9 mg/100 ml, a small decrease in plasma calcium concentration evoked a pronounced increase in secretion rate. A maximal secretion rate of about 5.5 ng/kg/min was attained at a plasma calcium concentration of approximately 7.5 mg/100 ml and it was not increased by more severe hypocalcemia. These observations confirm the sigmoidal relationship between PTH secretion rate and plasma calcium concentration which was previously suggested by measurement of PTH concentration in peripheral plasma of hypocalcemic, parturient cows.
采用一种技术对16头麻醉后的小牛甲状旁腺激素（PTH）分泌率进行了测定，该技术包括对甲状旁腺静脉血进行放射免疫测定，在规定时间间隔内采集甲状旁腺静脉血并进行容量测量。这些小牛的年龄在2至14周之间。通过向颈静脉输注氯化钙或乙二胺四乙酸二钠（Na2EDTA）溶液来改变血浆钙浓度。当血浆钙浓度超过10.5mg/100ml时，尽管诱发了高钙血症，但仍维持0.3ng/kg/min的基础、不可抑制的分泌率。在血浆钙浓度介于9至10.5mg/100ml之间时，观察到分泌率有轻微变化。低于9mg/100ml时，血浆钙浓度的小幅下降会引起分泌率的显著增加。在血浆钙浓度约为7.5mg/100ml时达到约5.5ng/kg/min的最大分泌率，更严重的低钙血症并未使其增加。这些观察结果证实了PTH分泌率与血浆钙浓度之间的S形关系，这一关系先前在低钙血症的分娩母牛外周血浆中PTH浓度的测量中已被提出。
