Bruchovsky N, Rennie P S, Vanson A
Biochim Biophys Acta. 1975 Jun 25;394(2):248-66. doi: 10.1016/0005-2736(75)90263-1.
Experiments were performed to assess the effect of intracellular androgen metabolism and the availability of cytoplasmic receptors on the concentration of androgens and androgen receptors in nuclei of prostatic cells. It was found that androgens are incorporated into the nucleus by a regulated, selective process which appears to limit the type and amount of androgen transported across the nuclear membrane. The metabolic conversion of testosterone to dihydrotestosterone which takes place in cytoplasm does not reduce transport and, very likely, affects only the ratio of testosterone and dihydrotestosterone transferred into the nucleus. In vivo, when the intranuclear concentration of androgens approaches 250 nM (8 pmol per mg DNA), an apparent concentration ceiling is reached even in the presence of a downward concentration gradient that would be expected to promote further transport across the nuclear membrane. This finding strongly suggests that in vivo the nuclear membrane acts as a barrier to the passage of androgens and, therefore, mitigates against the possibility that passive diffusion is an important mechanism of afferent transport of androgens into the nucleus. The ability of the nucleus to concentrate testosterone and dihydrotestosterone was clearly demonstrated in vivo when cytoplasmic concentrations of androgens of approximately 20 nM were accompanied by intranuclear concentrations in the vicinity of 250 nM. Since the measured concentration of testosterone and dihydrotestosterone in prostate of several species fall within the 5-20 nM range, it is evident that androgen concentrations in the nucleus as high as 250 nM may be typical of the physiological steady state. At the latter concentration the nucleus contains 60 000 androgen molecules: in approximate terms one third of this total is bound to a large molecular weight component of the nucleus, one third is bound to a 3.3 S receptor and one third is free or loosely bound. Since 60 000 androgen molecules and 20 000 receptor molecules appear in the nucleus before transport stops, it seems that the quantity of 4.4 S cytoplasmic receptor estimated at 174 plus or minus 24 pmol per mg protein (equivalent to about 8000 molecules per cell) is insufficient to account for the total influx of androgens and androgen receptors into the nucleus. Thus, although these results support the view that cytoplasmic receptors and the capacity to transport androgens are closely linked phenotypic markers of intracellular steroid hormone action, they suggest that the control of androgen concentration in the nucleus is achieved in a more intricate fashion than simply through a dependence on the presumed translocation of 4.4 S androgen-receptor complex into the nucleus.
进行了实验以评估细胞内雄激素代谢和细胞质受体的可利用性对前列腺细胞核中雄激素和雄激素受体浓度的影响。结果发现，雄激素通过一个受调控的选择性过程进入细胞核，该过程似乎限制了跨核膜转运的雄激素的类型和数量。睾酮在细胞质中代谢转化为二氢睾酮并不会减少转运，而且很可能仅影响转运到细胞核中的睾酮和二氢睾酮的比例。在体内，当细胞核内雄激素浓度接近250 nM（每毫克DNA 8 pmol）时，即使存在预期会促进进一步跨核膜转运的浓度梯度下降，也会达到一个明显的浓度上限。这一发现强烈表明，在体内核膜是雄激素通过的屏障，因此，减少了被动扩散是雄激素传入细胞核的重要机制的可能性。当细胞质中雄激素浓度约为20 nM时，细胞核内浓度在250 nM左右，这清楚地证明了细胞核在体内浓缩睾酮和二氢睾酮的能力。由于在几种物种的前列腺中测得的睾酮和二氢睾酮浓度在5 - 20 nM范围内，显然细胞核中高达250 nM的雄激素浓度可能是生理稳态的典型特征。在后者浓度下，细胞核含有60000个雄激素分子：大致来说，总数的三分之一与细胞核的一个大分子成分结合，三分之一与一个3.3 S受体结合，三分之一是游离的或松散结合的。由于在转运停止前细胞核中出现60000个雄激素分子和20000个受体分子，似乎每毫克蛋白质估计为174±24 pmol（相当于每个细胞约8000个分子）的4.4 S细胞质受体数量不足以解释雄激素和雄激素受体进入细胞核的总流入量。因此，尽管这些结果支持细胞质受体以及转运雄激素的能力是细胞内类固醇激素作用的密切相关的表型标记这一观点，但它们表明细胞核中雄激素浓度的控制是以一种比简单地依赖假定的4.4 S雄激素 - 受体复合物转运到细胞核更为复杂的方式实现的。
