Goldman D W, Gifford L A, Olson D M, Goetzl E J
J Immunol. 1985 Jul;135(1):525-30.
The uptake of Quin-2 by human polymorphonuclear (PMN) leukocytes permitted accurate fluorimetric quantification of the cytosolic concentration of intracellular calcium [( Ca+2]in), without altering the expression of the two subsets of leukotriene B4 (LTB4) receptors, as assessed by the binding of [3H]LTB4. Chemotactic concentrations of LTB4 elicited a rapid increase in [Ca+2]in, which reached a peak within 0.6 to 1 min and then decayed back to baseline levels by 6 to 10 min. The maximal increase and the half-maximal increase in [Ca+2]in were achieved by LTB4 at mean concentrations of 5 X 10(-10) M and 2 X 10(-10) M, respectively, where the binding of LTB4 to high-affinity receptors predominates. A rank order of potency of LTB4 greater than 5(S),12(S)-6-trans-LTB4 greater than 12(S)-LTB4 was established for the elicitation of increases in [Ca+2]in, which reflects the binding of the isomers to low-affinity receptors. PMN leukocytes were preincubated with 10(-8) M LTB4 to induce chemotactic deactivation, which eliminates the expression of high-affinity receptors without altering the expression of the low-affinity receptors for LTB4. LTB4 elicited an increase in [Ca+2]in in the deactivated PMN leukocytes with an EC50 of 3 X 10(-8) M, which is similar to the Kd for LTB4 binding to the low-affinity receptors. Two lines of cultured human leukemic cells, IM-9 and HL-60, did not bind LTB4 specifically and did not show any change in [Ca+2]in upon the addition of 3 X 10(-8) M LTB4. The HL-60 human promyelocytic leukemia cell line was induced to differentiate in 1% dimethyl sulfoxide to leukocytes with more mature myelocytic characteristics. Differentiated HL-60 cells expressed an average of 54,000 low-affinity receptors for LTB4 per cell with an average dissociation constant of 7.3 X 10(-8) M and concurrently developed the capacity to respond to LTB4 with an increase in [Ca+2]in. The binding of LTB4 to either high-affinity or low-affinity receptors appears to be sufficient to initiate an increase in [Ca+2]in in human PMN leukocytes and differentiated HL-60 cells. The specificity of LTB4 receptors in transducing maximum increases in [Ca+2]in is determined by the subset of receptors that predominate as a result of the concentration of LTB4 and the state of the responding cells.
人多形核（PMN）白细胞对喹啉 - 2的摄取，使得能够通过荧光法准确测定细胞内钙（[Ca +2]in）的胞质浓度，同时不会改变白三烯B4（LTB4）受体两个亚群的表达，这通过[3H]LTB4的结合来评估。趋化浓度的LTB4引起[Ca +2]in迅速增加，在0.6至1分钟内达到峰值，然后在6至10分钟内衰减回基线水平。LTB4分别在平均浓度为5×10（-10）M和2×10（-10）M时实现[Ca +2]in的最大增加和半最大增加，此时LTB4与高亲和力受体的结合占主导。建立了LTB4大于5（S），12（S）-6 - 反式 - LTB4大于12（S）-LTB4诱导[Ca +2]in增加的效力等级顺序，这反映了异构体与低亲和力受体的结合。PMN白细胞用10（-8）M LTB4预孵育以诱导趋化失活，这消除了高亲和力受体的表达，而不改变LTB4低亲和力受体的表达。LTB4在失活的PMN白细胞中引起[Ca +2]in增加，EC50为3×10（-8）M，这与LTB4与低亲和力受体结合的Kd相似。两株培养的人白血病细胞系IM - 9和HL - 60不特异性结合LTB4，并且在加入3×10（-8）M LTB4后[Ca +2]in没有任何变化。HL - 60人早幼粒细胞白血病细胞系在1％二甲基亚砜中诱导分化为具有更成熟髓细胞特征的白细胞。分化的HL - 60细胞平均每个细胞表达54,000个LTB4低亲和力受体，平均解离常数为7.3×10（-8）M，同时发展出对LTB4作出反应使[Ca +2]in增加的能力。LTB4与高亲和力或低亲和力受体的结合似乎足以引发人PMN白细胞和分化的HL - 60细胞中[Ca +2]in的增加。LTB4受体在转导[Ca +2]in最大增加中的特异性由由于LTB4浓度和反应细胞状态而占主导的受体亚群决定。
