Aldosterone Decreases Vasopressin-Stimulated Water Reabsorption in Rat Inner Medullary Collecting Ducts.

Aldosterone indirectly regulates water reabsorption in the distal tubule by regulating sodium reabsorption. However, the direct effect of aldosterone on vasopressin-regulated water and urea permeability in the rat inner medullary collecting duct (IMCD) has not been tested. We investigated whether aldosterone regulates osmotic water permeability in isolated perfused rat IMCDs. Adding aldosterone (500 nM) to the bath significantly decreased osmotic water permeability in the presence of vasopressin (50 pM) in both male and female rat IMCDs. Aldosterone significantly decreased aquaporin-2 (AQP2) phosphorylation at S256 but did not change it at S261. Previous studies show that aldosterone can act both genomically and non-genomically. We tested the mechanism by which aldosterone attenuates osmotic water permeability. Blockade of gene transcription with actinomycin D did not reverse aldosterone-attenuated osmotic water permeability. In addition to AQP2, the urea transporter UT-A1 contributes to vasopressin-regulated urine concentrating ability. We tested aldosterone-regulated urea permeability in vasopressin-treated IMCDs. Blockade of gene transcription did not reverse aldosterone-attenuated urea permeability. In conclusion, aldosterone directly regulates water reabsorption through a non-genomic mechanism. Aldosterone-attenuated water reabsorption may be related to decreased trafficking of AQP2 to the plasma membrane. There may be a sex difference apparent in the inhibitory effect of aldosterone on water reabsorption in the inner medullary collecting duct. This study is the first to show a direct effect of aldosterone to inhibit vasopressin-stimulated osmotic water permeability and urea permeability in perfused rat IMCDs.

Mentha longifolia alleviates experimentally induced angina via decreasing cardiac load.

Angina occurs due to imbalance between heart oxygen demand and supply and is associated with serious morbidity and mortality. Here, the possible antianginal effect of Mentha longifolia extract was studied in experimental model of angina. Aerial parts of M. longifolia were extracted, standardized, and given to rats three days before angina. Heart hemodynamics and conductivity were recorded by microtip catheter and surface electrodes. M. longifolia extract significantly alleviated the sustained decline in cardiac contractility after vasopressin exposure. However, M. longifolia did not affect the impaired cardiac dilation after vasopressin. Heart rate was significantly decreased after vasopressin exposure in rats treated with M. longifolia compared with untreated animals. In addition, M. longifolia produced more increase in systolic and diastolic durations after vasopressin exposure compared with untreated animals. Moreover, the plant extract alleviated the ST height changes during vasopressin injection. M. longifolia extract alleviates impaired cardiac function associated with angina through decreasing heart work. PRACTICAL APPLICATIONS: The present study is the first to study the effect of M. longifolia in an experimental model of angina. M. longifolia alleviated the impaired cardiac contractility associated with angina exposure. The antianginal effect of M. longifolia could be through reducing cardiac load. This can be concluded from the decrease in heart rate and the systolic and diastolic cycles elongation after exposure to vasopressin in animals pretreated with M. longifolia. This helps in reducing the associated cardiac ischemia upon exposure to vasopressin as indicated by ST change. This could provide new directions in the management of the serious angina disease.

Two-channel gastric electrical stimulation accelerates delayed gastric emptying induced by vasopressin.

The aim of this study was to investigate the effects of two-channel gastric electrical stimulation (GES) on delayed gastric emptying, gastric dysrhythmias, and motion sickness-like symptoms induced by vasopressin. Seven dogs implanted with four pairs of gastric electrodes and a duodenal cannula were studied in four randomized sessions (saline, vasopressin, single-channel GES, and two-channel GES). The experiment in each session was conducted sequentially as follows: 30-min baseline, ingestion of a liquid meal, 30-min iv infusion of vasopressin or saline, and two 30-min postprandial recordings. In the GES sessions, GES was applied via the first pair of electrodes for single-channel GES or the first and third pairs of electrodes for two-channel GES. Gastric emptying was collected every 15 min via the cannula for a period of 90 min. Results were as follows. (1) Vasopressin induced gastric dysrhythmias, motion sickness-like symptoms, and delayed gastric emptying (P < 0.01, ANOVA). (2) GES normalized gastric dysrhythmias (P < 0.01) but showed no effects on vasopressin-induced emetic response. (3) Two-channel GES improved delayed gastric emptying induced by vasopressin. In comparison with the vasopressin session, two-channel GES, but not single-channel GES, significantly increased gastric emptying at 30 min (43.9+/-12.6 vs. 27.5+/-7.7%; P < 0.03), 60 min (75.3+/-15.1 vs. 54.0+/-17.8%; P < 0.05), and 90 min (91.6+/-9.8 vs. 80.3+/-9.0%; P < 0.05). GES with long pulses is able to normalize gastric dysrhythmias. Two-channel GES improves delayed gastric emptying induced by vasopressin.

Effects of intestinal electrical stimulation on intestinal dysrhythmia and symptoms in dogs.

The aim of this study was to investigate the effect of intestinal electrical stimulation on small intestinal dysrhythmia and motion sickness-like symptoms induced by vasopressin. Female dogs chronically implanted with two pairs of electrodes on jejunum serosa were used in a four-session study. Saline and vasopressin were infused in sessions 1 and 2, respectively. Sessions 3 and 4 were the same as session 2, except a long- or short-pulse intestinal electrical stimulation was applied on the proximal pair of electrodes. Intestinal slow waves and motion sickness-like symptoms were recorded in each session. Results were as follows. (1) Vasopressin induced intestinal dysrhythmia, uncoupling of slow waves, and vomiting and motion sickness-like symptoms (P < 0.05, ANOVA). (2) Intestinal electrical stimulation with long pulses, but not short pulses, was capable of preventing vasopressin-induced intestinal dysrhythmia. (3) Intestinal electrical stimulation with short pulses, but not long pulses, prevented vomiting and the motion sickness-like symptoms. It is concluded that vasopressin induces intestinal dysrhythmia. Long-pulse intestinal stimulation normalizes vasopressin-induced intestinal slow-wave abnormalities with no improvement in symptoms. Short-pulse stimulation prevents emetic symptoms induced by vasopressin but has no effect on slow waves. These data suggest different mechanisms involved with different methods of intestinal stimulation.

Gastric stimulation is effective in reversing vasopressin induced gastroparesis.

UNLABELLED: The aim of this study was to determine the most effective current parameters reversing vasopressin (VP) induced gastroparesis by gastric electrical stimulation IGES). METHODS: Twenty male healthy Wistar rats were included into the study (weight 227 +/- 24 g). Animals were subjected to gastric fistula placement and implantation of two monopolar electrodes for EGG-studies and GES. After 5 days of recovery VP was applied (terlipressin 0.1 mg/kg i.p.) The gastric motility was measured by means of balloon introduced into the stomach through the fistula. The gastric electrical and motor activity were recorded by the PowerLab/8SP system and software. Electrical signals were cleared by 3000 AC/DC differential amplifier A-M System Inc. Gastric electrical stimulation (GES) was generated by Zimmer stimulator SINUS5. The following currents: S01 (monopolar): ampl 2.2 mA, freq 29 Hz, on/off 1 s / 10 s; S02 (bipolar): ampl 2.2 mA, freq 29 Hz, on/off 1s/10s: S03 (monopolar): ampl 2.2 mA, freq 0.5 Hz: S04 (monopolar): ampl 2.2 mA, freq 34 Hz, on/off 5.5 s/15 s were used. RESULTS: The phasic contractions almost disappeared and amplitude decreased from 12 +/- 5 to 2.9 +/- 1.5 cm H20. The motility index decreased from 276,3 +/- 76.4 to 154.6 +/- 63 cm H2O x s/min. GES S01-S04 increased motility index to: 167.6 +/- 60.8: 155.1 +/- 89.3; 170.3 +/- 92.3: 301.9 +/- 70.5 cm H2O x s/min respectively. The frequency of gastric slow wave increased from 0.04 +/- 0.02 to 0.07 +/- 0.02 Hz after VP administration. GES S01-S04 reversed VP induced increase of slow wave frequency to 0.06 +/- 0.02, 0.055 +/- 0.02, 0.06 +/- 0.01 and 0.04 +/- 0.02 Hz, respectively. CONCLUSIONS: This effectiveness of local GES and the pressure pattern of induced gastroparesis suggest peripheral complex inhibitory-excitatory action of vasopressin on gastric smooth muscles. The mechanism of this action may involve the enteric nervous system, gastric and vasal smooth muscles. The most effective in reversing VP induced functional gastroparesis is high frequency current applied in timing of the natural slow wave.

Octreotide for acute esophageal variceal bleeding: a meta-analysis.

BACKGROUND & AIMS: Studies of octreotide have not demonstrated a consistent benefit in efficacy or safety compared with conventional therapies. This study statistically pooled existing trials to evaluate the safety and efficacy of octreotide for esophageal variceal hemorrhage. METHODS: We identified randomized trials of octreotide for variceal hemorrhage from computerized databases, scientific meeting abstracts, and the manufacturer of octreotide. Blinded reviewers abstracted the data, and a meta-analysis was performed. RESULTS: Octreotide improved control of esophageal variceal hemorrhage compared with all alternative therapies combined (relative risk [RR], 0.63; 95% confidence interval [CI], 0.51-0.77); vasopressin/terlipressin (RR, 0.58; 95% CI, 0.42-0.81); or no additional intervention/placebo (among patients that received initial sclerotherapy/banding before randomization) (RR, 0.46; 95% CI, 0.32-0.67). Octreotide had comparable efficacy to immediate sclerotherapy for control of bleeding (RR, 0.94; 95% CI, 0.55-1.62), fewer major complications than vasopressin/terlipessin (RR, 0.31; 95% CI, 0.11-0.87), and a complication profile comparable to no intervention/placebo (RR, 1.06; 95% CI, 0.72-1.55). No specific alternative therapy demonstrated a mortality benefit. CONCLUSIONS: These results favor octreotide over vasopressin/terlipressin in the control of esophageal variceal bleeding and suggest it is a safe and effective adjunctive therapy after variceal obliteration techniques. Trials are needed to determine the optimal dose, route, and duration of octreotide treatment.

Torsade de pointes in a patient receiving intravenous vasopressin.

A patient experienced hypertension, bradycardia, QT prolongation, and multiple episodes of torsade de pointes while receiving an iv vasopressin infusion. The dysrhythmias were attributed to vasopressin, but may have been potentiated by hypomagnesemia. Upon vasopressin discontinuation, ECG findings returned to normal before magnesium supplementation. Vasopressin may contribute to the development of torsade de pointes.