Knepper M A, Burg M B
Am J Physiol. 1981 Nov;241(5):F502-8. doi: 10.1152/ajprenal.1981.241.5.F502.
To investigate whether mineralocorticoids affect the intrinsic capacity of the proximal tubule to absorb sodium and fluid, rabbits were chronically treated a number of ways to systematically vary plasma concentrations of mineralocorticoid hormones. The rate of fluid absorption and tubule dimensions were measured in superficial S2 segments from these rabbits. Chronic administration of deoxycorticosterone acetate (DOCA) was associated with a 67% increase in fluid absorption and a 29% increase in cell volume per unit tubule length. However, neither adrenalectomy nor low sodium diet significantly affected either fluid absorption or cell volume. Furthermore, marked dietary sodium restriction prevented the response to DOCA. We conclude that the DOCA-induced increases in fluid absorption and cell volume do not result from a direct stimulation of the proximal tubular cells by the steroid but more likely are responses to systemic effects of DOCA administration that are dependent on the level of sodium intake. Thus, we find no evidence for a direct mineralocorticoid stimulation of sodium and fluid transport by the S2 portion of the proximal tubule.
为研究盐皮质激素是否影响近端小管吸收钠和液体的内在能力，采用多种方法对兔子进行长期处理，以系统改变盐皮质激素的血浆浓度。测定这些兔子浅表S2节段的液体吸收速率和小管尺寸。长期给予醋酸脱氧皮质酮（DOCA）会使液体吸收增加67%，单位小管长度的细胞体积增加29%。然而，肾上腺切除术和低钠饮食均未显著影响液体吸收或细胞体积。此外，显著的饮食钠限制可阻止对DOCA的反应。我们得出结论，DOCA引起的液体吸收和细胞体积增加并非由类固醇直接刺激近端小管细胞所致，而更可能是对DOCA给药的全身效应的反应，这种效应依赖于钠摄入水平。因此，我们没有发现证据表明盐皮质激素直接刺激近端小管S2部分的钠和液体转运。
