Renal function and the effect of oxytocin and vasopressin replacement have been examined in anaesthetized male neurohypophysectomized rats. 2. Rates of urine flow were higher but sodium excretion markedly lower in neurohypophysectomized rats than in intact animals receiving hypotonic saline infusion (33.8 +/- 2.3 vs. 27.0 +/- 0.7 ml and 472 +/- 84 vs. 1946 +/- 124 mumol respectively for the third to sixth hour of study). 3. In intact animals, mean arterial blood pressure stabilized at 106 mmHg. Haematocrit (46%) remained stable but glomerular filtration rates declined slightly over the 8 h of study to 2.5 +/- 0.2 ml/h. These values in neurohypophysectomized rats did not differ significantly from those in intact rats. 4. Although plasma corticosterone levels (54 +/- 13 ng/ml) did not differ significantly from those in intact rats, neurohypophysectomy was associated with greatly reduced aldosterone concentration (0.12 +/- 0.03 vs. 0.76 +/- 0.04 ng/ml). Trace levels of vasopressin (0.17 +/- 0.03 microunit/ml) were found in neurohypophysectomized rat plasma. 5. Oxytocin administration at 15 microunits/min, which produced plasma hormone levels of 1.62 +/- 0.19 microunit/ml, had no detectable effect on sodium excretion but increased urine flow. Arginine vasopressin administration (12 microunits/min) inducing plasma levels of 1.24 +/- 0.08 microunit/ml, reduced urine flow by 80% and produced a small increase in sodium excretion. 6. Concurrent administration of oxytocin (15 microunits/min) potentiated the natriuretic response to vasopressin (12 microunits/min). Total sodium excretion during the 3 h combined hormone infusion (1256 +/- 149 mumol) greatly exceeded that in animals receiving vasopressin alone (549 +/- 132 mumol) and approached that observed in intact animals (1946 +/- 124 mumol). Combined hormone administration at the lower rate of 5 microunits/min oxytocin and 4 microunits/min vasopressin produced a similar large increment in sodium excretion. 7. It is concluded that replacement of both neurohypophysial hormones, at plasma levels within the physiological range, largely reverses the renal sodium retention of neurohypophysectomized rats, oxytocin considerably potentiating the natriuretic action of vasopressin. This synergism between the two neurohypophysial peptides to promote salt excretion may be an important component of the non-steroidal management of sodium.
摘要
对麻醉状态下的雄性垂体后叶切除大鼠的肾功能以及催产素和加压素替代治疗的效果进行了研究。2. 垂体后叶切除大鼠的尿流率较高，但钠排泄量明显低于接受低渗盐水输注的完整动物（研究的第三至第六小时，分别为33.8±2.3 vs. 27.0±0.7 ml以及472±84 vs. 1946±124 μmol）。3. 在完整动物中，平均动脉血压稳定在106 mmHg。血细胞比容（46%）保持稳定，但肾小球滤过率在8小时的研究过程中略有下降，降至2.5±0.2 ml/h。垂体后叶切除大鼠的这些值与完整大鼠的这些值无显著差异。4. 尽管血浆皮质酮水平（54±13 ng/ml）与完整大鼠的无显著差异，但垂体后叶切除术与醛固酮浓度大幅降低有关（0.12±0.03 vs. 0.76±0.04 ng/ml）。在垂体后叶切除大鼠血浆中发现了微量的加压素（0.17±0.03微单位/ml）。5. 以15微单位/分钟的速度给予催产素，使血浆激素水平达到1.62±0.19微单位/ml时，对钠排泄无明显影响，但增加了尿流。给予精氨酸加压素（12微单位/分钟）使血浆水平达到1.24±0.08微单位/ml时，尿流减少了80%，并使钠排泄略有增加。6. 同时给予催产素（15微单位/分钟）可增强对加压素（12微单位/分钟）的利钠反应。在联合激素输注的3小时内，总钠排泄量（1256±149 μmol）大大超过单独接受加压素的动物（549±132 μmol），并接近完整动物中观察到的水平（1946±124 μmol）。以5微单位/分钟的催产素和4微单位/分钟的加压素较低速率联合给予激素，也使钠排泄有类似的大幅增加。7. 得出的结论是，在生理范围内的血浆水平下，同时替代两种神经垂体激素在很大程度上可逆转垂体后叶切除大鼠的肾钠潴留，催产素可显著增强加压素的利钠作用。这两种神经垂体肽之间促进排盐的协同作用可能是钠的非甾体管理的一个重要组成部分。
