Costlow M E, Rodgers Q E
Exp Cell Res. 1986 Mar;163(1):159-64. doi: 10.1016/0014-4827(86)90568-9.
Primary cultures of carcinogen-induced rat mammary tumors incubated at 37 degrees C with 125I-labeled ovine prolactin (5 ng/ml) accumulate intact prolactin. A steady state is reached at 24--48 h and loss of accumulated prolactin is slow t1/2 24 h). Accumulated prolactin is rapidly released when cryptic prolactin receptors are unmasked by energy depletion, suggesting that accumulated prolactin and cryptic receptors reside in the same cellular compartment. Under normal conditions, the accumulated prolactin is released slowly and is partially degraded. Subcellular fractionation on discontinuous sucrose gradients indicates that cryptic receptors reside in vesicle fractions (p less than or equal to 1.16). After energy depletion, the unmasked receptors are in cell surface membrane fractions (p = 1.18-1.20). Prolactin accumulation within receptor-containing vesicles in mammary tumor cells may account for their increased growth sensitivity (compared with normal mammary cells) to low physiologic levels of prolactin.
将致癌物诱导的大鼠乳腺肿瘤原代培养物在37℃下与125I标记的绵羊催乳素（5纳克/毫升）一起孵育，可积累完整的催乳素。在24 - 48小时达到稳态，积累的催乳素损失缓慢（半衰期为24小时）。当隐匿性催乳素受体因能量耗竭而暴露时，积累的催乳素会迅速释放，这表明积累的催乳素和隐匿性受体存在于同一细胞区室中。在正常情况下，积累的催乳素释放缓慢且部分降解。在不连续蔗糖梯度上进行亚细胞分级分离表明，隐匿性受体存在于囊泡级分中（p≤1.16）。能量耗竭后，暴露的受体存在于细胞表面膜级分中（p = 1.18 - 1.20）。乳腺肿瘤细胞中含受体囊泡内的催乳素积累可能解释了它们（与正常乳腺细胞相比）对低生理水平催乳素的生长敏感性增加。
