Shah G V, Chien J, Sun Y P, Puri S, Ravindra R
Department of Surgery, University of Kansas Medical Center, Kansas City 66160, USA.
Endocrinology. 1999 Sep;140(9):4281-91. doi: 10.1210/endo.140.9.6995.
Previous studies have shown that CT-like immunoreactive peptide(s) (pit-CT) is synthesized by the anterior pituitary (AP) gland, and exogenously added salmon(s) CT inhibits PRL release and PRL gene transcription in cultured AP cells. Anti-sCT serum, which immunoreacts with pit-CT, stimulates PRL secretion, suggesting pit-CT is a physiologically relevant PRL-inhibiting hormone. Using proliferating cell nuclear antigen (PCNA) staining and 5-bromo-2'deoxyuridine (BrdU) incorporation into newly replicated DNA, the effect of calcitonin (CT) on cellular proliferation in the rat anterior pituitary gland (AP) was examined. CT significantly attenuated PCNA-immunopositive as well as BrdU-positive AP cell populations in dispersed rat AP cells. A second series of experiments tested the effects of CT on AP cell proliferation in vivo. OVX + E2 rats were injected with 200 microg CT (iv), the rats killed at various time points, and the APs were processed for BrdU staining. CT inhibited BrdU incorporation at all time points up to 15 h after the injection, and this inhibitory effect was reversed at later time points. The effect of CT was concentration dependent, and a maximal inhibition was observed 10 h after the CT injection. Subsequent experiments identified CT-responsive AP cell populations using double immunofluorescence for BrdU and either PRL or FSH. The number of BrdU-labeled lactotropes in the AP gland declined by 74% in the CT-treated rats. Neutralization of endogenous pit-CT by passive immunization with anti-sCT serum caused a 2-fold increase in AP cell proliferation. These results suggest an important role for the endogenous pit-CT in regulation of lactotrope population of the AP gland.
先前的研究表明，垂体CT样免疫反应性肽（pit-CT）由垂体前叶（AP）合成，外源性添加的鲑鱼降钙素（sCT）可抑制培养的AP细胞中催乳素（PRL）的释放及PRL基因转录。与pit-CT发生免疫反应的抗sCT血清可刺激PRL分泌，提示pit-CT是一种具有生理相关性的PRL抑制激素。利用增殖细胞核抗原（PCNA）染色及5-溴-2'-脱氧尿苷（BrdU）掺入新复制的DNA，研究了降钙素（CT）对大鼠垂体前叶（AP）细胞增殖的影响。CT显著减少了分散的大鼠AP细胞中PCNA免疫阳性及BrdU阳性的AP细胞群体。另一系列实验检测了CT对体内AP细胞增殖的影响。给去卵巢+雌激素（OVX + E2）大鼠静脉注射200μg CT，在不同时间点处死大鼠，并对AP进行BrdU染色处理。CT在注射后长达15小时的所有时间点均抑制BrdU掺入，且这种抑制作用在随后的时间点被逆转。CT的作用呈浓度依赖性，在CT注射后10小时观察到最大抑制作用。随后的实验利用BrdU与PRL或促卵泡激素（FSH）的双重免疫荧光鉴定了对CT有反应的AP细胞群体。在CT处理的大鼠中，AP腺体内BrdU标记的催乳细胞数量减少了74%。用抗sCT血清进行被动免疫中和内源性pit-CT导致AP细胞增殖增加2倍。这些结果表明内源性pit-CT在调节AP腺催乳细胞群体中起重要作用。
