Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
BMC Complement Altern Med. 2012 Apr 11;12:40. doi: 10.1186/1472-6882-12-40.
In a previous study, we showed that a saponin mixture isolated from the roots of Ampelozizyphus amazonicus Ducke (SAPAaD) reduces urine excretion in rats that were given an oral loading of 0.9 % NaCl (4 ml/100 g body weight). In the present study, we investigated whether atrial natriuretic peptides (ANP) and renal ATPases play a role in the SAPAaD- induced antidiuresis in rats.
To evaluate the effect of SAPAaD on furosemide-induced diuresis, Wistar rats (250-300 g) were given an oral loading of physiological solution (0.9 % NaCl, 4 ml/100 g body weight) to impose a uniform water and salt state. The solution containing furosemide (Furo, 13 mg/kg) was given 30 min after rats were orally treated with 50 mg/kg SAPAaD (SAPAaD + Furo) or 0.5 ml of 0.9 % NaCl (NaCl + Furo). In the SAPAaD + NaCl group, rats were pretreated with SAPAaD and 30 min later they received the oral loading of physiological solution. Animals were individually housed in metabolic cages, and urine volume was measured every 30 min throughout the experiment (3 h). To investigate the role of ANP and renal Na(+) pumps on antidiuretic effects promoted by SAPAaD, rats were given the physiological solution (as above) containing SAPAaD (50 mg/kg). After 90 min, samples of urine and blood from the last 30 min were collected. Kidneys and atria were also removed after previous anesthesia. ANP was measured by radioimmunoassay (RIA) and renal cortical activities of Na(+)- and (Na(+),K(+))-ATPases were calculated from the difference between the [32P] Pi released in the absence and presence of 1 mM furosemide/2 mM ouabain and in the absence and presence of 1 mM ouabain, respectively.
It was observed that SAPAaD inhibited furosemide-induced diuresis (at 90 min: from 10.0 ± 1.0 mL, NaCl + Furo group, n = 5, to 5.9 ± 1.0 mL, SAPAaD + Furo group n = 5, p < 0.05), increased both Na(+)-ATPase (from 25.0 ± 5.9 nmol Pi.mg(-1).min(-1), control, to 52.7 ± 8.9 nmol Pi.mg(-1).min(-1), p < 0.05) and (Na(+),K(+))-ATPase (from 47.8 ± 13.3 nmol Pi.mg(-1).min(-1), control, to 79.8 ± 6.9 nmol Pi .mg(-1).min(-1), p < 0.05) activities in the renal cortex. SAPAaD also lowered urine ANP (from 792 ± 132 pg/mL, control, to 299 ± 88 pg/mL, p < 0.01) and had no effect on plasma or atrial ANP.
We concluded that the SAPAaD antidiuretic effect may be due to an increase in the renal activities of Na(+)- and (Na(+),K(+))-ATPases and/or a decrease in the renal ANP.
在之前的研究中，我们发现从亚马逊酒饼树（Ampelozizyphus amazonicus Ducke）的根部分离出的皂素混合物（SAPAaD）可减少口服 0.9%NaCl（4ml/100g 体重）负荷的大鼠的尿排量。在本研究中，我们研究了心钠肽（ANP）和肾 ATP 酶是否在 SAPAaD 诱导的大鼠抗利尿作用中起作用。
为了评估 SAPAaD 对呋塞米诱导的利尿作用的影响，给予 Wistar 大鼠（250-300g）口服生理盐水（0.9%NaCl，4ml/100g 体重）以形成均匀的水盐状态。在大鼠口服 50mg/kg SAPAaD（SAPAaD+Furo）或 0.5ml 0.9%NaCl（NaCl+Furo）30min 后，给予含呋塞米（Furo，13mg/kg）的溶液。在 SAPAaD+NaCl 组中，大鼠先给予 SAPAaD 预处理，30min 后给予口服生理盐水负荷。动物单独饲养在代谢笼中，整个实验过程（3h）每 30min 测量一次尿量。为了研究 SAPAaD 促进的抗利尿作用中 ANP 和肾 Na+泵的作用，大鼠给予含有 SAPAaD（50mg/kg）的生理盐水（如上所述）。90min 后，收集最后 30min 的尿液和血液样本。在先前麻醉后还取出肾脏和心房。通过放射免疫测定（RIA）测量 ANP，并分别从无和有 1mM 呋塞米/2mM 哇巴因以及无和有 1mM 哇巴因的情况下计算肾皮质 Na+-和（Na+，K+）-ATP 酶的[32P]Pi 释放量来计算活性。
结果表明，SAPAaD 抑制了呋塞米诱导的利尿作用（90min 时：从 10.0±1.0mL，NaCl+Furo 组，n=5，到 5.9±1.0mL，SAPAaD+Furo 组，n=5，p<0.05），增加了肾皮质中的 Na+-ATP 酶（从 25.0±5.9nmolPi.mg-1.min-1，对照，到 52.7±8.9nmolPi.mg-1.min-1，p<0.05）和（Na+，K+）-ATP 酶（从 47.8±13.3nmolPi.mg-1.min-1，对照，到 79.8±6.9nmolPi.mg-1.min-1，p<0.05）的活性。SAPAaD 还降低了尿 ANP（从 792±132pg/mL，对照，到 299±88pg/mL，p<0.01），但对血浆或心房 ANP 无影响。
我们得出结论，SAPAaD 的利尿作用可能是由于肾 Na+-和（Na+，K+）-ATP 酶活性的增加和/或肾 ANP 的减少所致。
