Henry H L, Cunningham N S, Noland T A
Endocrinology. 1983 Dec;113(6):1942-9. doi: 10.1210/endo-113-6-1942.
The development of refractoriness of the cAMP response to PTH in primary cultures of chick kidney cells and recovery from the refractory state was investigated. When cells were preincubated with bovine PTH1-34, complete refractoriness to a subsequent challenge with the hormone developed within 2 h and at hormone concentrations as low as 5 ng/ml. The ability of PTH to stimulate activation of cAMP-dependent protein kinase was also abolished by preincubation with the hormone. When cells were desensitized and then incubated in hormone-free medium, recovery of the cAMP response began within an hour and was maximal, but not complete (80%) after 16 h. Cycloheximide did not affect either desensitization or the rate or extent of recovery from the refractory state. Low concentrations of forskolin (2.5 X 10(-7) M) greatly enhanced cAMP production stimulated by PTH and higher concentrations (10(-6) - 10(-4) M) stimulated rates of cAMP production 50 times those obtained with PTH alone. Preincubation with forskolin did not bring about desensitization to PTH nor did preincubation with PTH affect the subsequent response to forskolin. The half-life of biologically active bovine PTH1-34 in chick kidney cell culture was approximately 12 h and the rate of its removal was not significantly altered during a 20-h incubation period. The results suggest that desensitization of chick kidney cells to PTH is not suggest that desensitization of chick kidney cells to PTH is not brought about by cAMP generation itself, is not primarily dependent on protein synthesis, and does not involve a change in the rate of removal of biologically active hormone from the medium. In addition, recovery of the cAMP response to PTH also does not require new protein synthesis. These results are compatible with a mechanism of desensitization which occurs at the level of the receptor or hormone-receptor coupling to adenyl cyclase.
研究了鸡肾细胞原代培养物中cAMP对甲状旁腺激素（PTH）反应的不应性发展以及从不应状态的恢复情况。当细胞与牛PTH1 - 34预孵育时，在2小时内且激素浓度低至5 ng/ml时，对随后激素刺激产生完全不应性。用该激素预孵育也消除了PTH刺激cAMP依赖性蛋白激酶激活的能力。当细胞脱敏后在无激素培养基中孵育时，cAMP反应在1小时内开始恢复，16小时后达到最大值，但未完全恢复（80%）。放线菌酮既不影响脱敏过程，也不影响从不应状态恢复的速率或程度。低浓度的福斯高林（2.5×10⁻⁷ M）极大地增强了PTH刺激的cAMP产生，而高浓度（10⁻⁶ - 10⁻⁴ M）刺激的cAMP产生速率是单独使用PTH时的50倍。用福斯高林预孵育不会导致对PTH脱敏，用PTH预孵育也不影响随后对福斯高林的反应。生物活性牛PTH1 - 34在鸡肾细胞培养物中的半衰期约为12小时，在20小时孵育期内其去除速率没有显著改变。结果表明，鸡肾细胞对PTH的脱敏不是由cAMP生成本身引起的，不主要依赖于蛋白质合成，也不涉及从培养基中去除生物活性激素的速率变化。此外，cAMP对PTH反应的恢复也不需要新的蛋白质合成。这些结果与在受体或激素 - 受体与腺苷酸环化酶偶联水平发生的脱敏机制相符。
