Kaplan S A, Barrett C T, Scott M L, Whitson R H
Endocrinology. 1984 Jun;114(6):2199-204. doi: 10.1210/endo-114-6-2199.
Insulin binding was studied in type II pneumocytes isolated from fetal rabbit lungs (27 days of gestation) and grown in monolayers in tissue culture. The mean high affinity receptor site number was 11.8 +/- 1.4 X 10(3) (+/-SEM)/cell, with a Kd of 0.45 +/- 0.07 nM (n = 6). Low affinity sites averaged 432 +/- 10.7 X 10(3)/cell, with a Kd of 45.6 +/- 11.8 nM. Incubation of the cells with 5 X 10(-10) M (Bu)2cAMP (DBcAMP) and 10(-3) M methylisobutylxanthine (MIX) for 18 h led to significant increases in the number of high affinity receptor sites and Kd (P = 0.025 and 0.05, respectively). Incubation of the cells with insulin (1 microgram/ml) for 18 h led to a significant diminution in the mean number of high affinity sites to 3.23 +/- 0.68 X 10(3)/cell (P = 0.0025). There was no significant change in the Kd of the high affinity sites. There was also no significant change in the number or affinity of the low affinity sites. When the cells were incubated with insulin in the presence of DBcAMP (5 X 10(-4) M) and MIX (10(-3) M), there was a significant increase in high affinity binding sites to a mean of 8.87 +/- 2.18 X 10(3)/cell (n = 4) compared to the value after incubation in the presence of insulin alone. There was no significant increase in the Kd of the high affinity sites. The following conclusions were drawn from these experiments. 1) Fetal type II pneumocytes possess receptors with high affinity for insulin. 2) The up-regulation of insulin receptor binding induced by high ambient concentrations of insulin in vivo in rabbit fetal lungs and circulating human monocytes does not occur in vitro when isolated pneumocytes are grown in tissue culture. 3) Insulin binding to type II pneumocytes is enhanced by DBcAMP and MIX. 4) Insulin down-regulation of receptor binding is significantly counteracted by DBcAMP and MIX.
对从妊娠27天的胎兔肺中分离出的II型肺细胞进行单层培养，并研究其胰岛素结合情况。高亲和力受体位点的平均数量为11.8±1.4×10³（±标准误）/细胞，解离常数（Kd）为0.45±0.07 nM（n = 6）。低亲和力位点平均为432±10.7×10³/细胞，Kd为45.6±11.8 nM。将细胞与5×10⁻¹⁰ M的双丁酰环磷腺苷（DBcAMP）和10⁻³ M的甲基异丁基黄嘌呤（MIX）孵育18小时，导致高亲和力受体位点的数量和Kd显著增加（P分别为0.025和0.05）。将细胞与胰岛素（1微克/毫升）孵育18小时，导致高亲和力位点的平均数量显著减少至3.23±0.68×10³/细胞（P = 0.0025）。高亲和力位点的Kd没有显著变化。低亲和力位点的数量或亲和力也没有显著变化。当细胞在DBcAMP（5×10⁻⁴ M）和MIX（10⁻³ M）存在的情况下与胰岛素孵育时，与仅在胰岛素存在下孵育后的数值相比，高亲和力结合位点显著增加至平均8.87±2.18×10³/细胞（n = 4）。高亲和力位点的Kd没有显著增加。从这些实验中得出了以下结论。1）胎儿II型肺细胞拥有对胰岛素具有高亲和力的受体。2）在兔胎儿肺和循环中的人单核细胞体内，高环境浓度胰岛素诱导的胰岛素受体结合上调，在体外分离的肺细胞进行组织培养时不会发生。3）DBcAMP和MIX可增强胰岛素与II型肺细胞的结合。4）DBcAMP和MIX可显著抵消胰岛素对受体结合的下调作用。
