Short communication
Endogenous bufadienolide mediates pressor response to ethanol withdrawal in rats

https://doi.org/10.1016/j.euroneuro.2007.05.006Get rights and content

Abstract

An endogenous natriuretic and vasoconstrictor Na/K-ATPase inhibitor, marinobufagenin (MBG), is implicated in NaCl-induced hypertension and in ethanol addiction. In rats, MBG suppresses voluntary alcohol intake, while immunization against MBG induces alcohol-seeking behavior. Since alcohol withdrawal is associated with elevation of blood pressure (BP) and renal sodium retention, we hypothesized that MBG mediates pressor response to ethanol withdrawal. In male Sprague–Dawley rats, forced ethanol intake (20% v/v, 2.8 ± 0.2 g/day for 7 days) did not affect BP and MBG excretion. Ethanol withdrawal was associated with a 21 mm Hg increase in BP, a 10% decrease in hematocrit, and a three-fold increase in renal MBG excretion. In vivo administration of anti-MBG antibody to rats prevented withdrawal-induced BP elevation. Therefore, MBG mediates pressor response to ethanol withdrawal, and may link mechanisms of ethanol dependence and hypertension.

Introduction

Chronic excessive alcohol consumption is a risk factor for hypertension (Di Gennaro et al., 2002). Endogenous digitalis-like inhibitors of the Na/K-ATPase (cardiotonic steroids — CTS) are implicated in the mechanisms of NaCl-sensitive hypertension (Haddy, 2006) and in ethanol tolerance (Bagrov et al., 2002). In the hypertensives, levels of CTS increase with an adaptive role to induce natriuresis via inhibition of the sodium pump in renal tubuli (Haddy, 2006). In addition, CTS inhibit the Na/K-ATPase in the vascular smooth muscle and potentiate vasoconstriction (Haddy, 2006). Marinobufagenin (MBG), a CTS belonging to a class of bufadienolides, exhibits high affinity to ouabain-resistant α-1 Na/K-ATPase isoform, the main sodium pump isoform in vascular sarcolemma and an exclusive sodium pump isoform in renal epithelium (Fedorova et al., 2002, Fedorova et al., 2005). Accordingly, in vivo MBG acts as a natriuretic and as a vasoconstrictor (Fedorova et al., 2002, Fedorova et al., 2005).

MBG is also implicated in the development of ethanol addiction in rats. In our previous experiments, administration of MBG to rats reduced voluntary ethanol consumption (Kashkin et al., 2002), while active immunization of rats against MBG facilitated ethanol-seeking behavior (Bagrov et al., 1999).

In alcoholics, ethanol withdrawal is associated with a pressor response and renal sodium retention (Di Gennaro et al., 2002). Since MBG is a natriuretic and a vasoconstrictor (Fedorova et al., 2002, Fedorova et al., 2005), and since this hormone exhibits anti-addictive properties (Bagrov et al., 2002), we hypothesized that MBG may mediate ethanol withdrawal-induced pressor response.

Section snippets

Methods

The protocol of the study has been approved by the Animal Care and Use Committee of the National Institute on Aging, NIH. Thirty male Sprague–Dawley rats (251 ± 2 g) (Charles River Laboratories, Inc., Wilmington, MA) were housed in individual cages with free access to standard chow and drinking water and with a 12:12-hour light/dark cycle (t = 21 °C).

Ethanol withdrawal was induced as reported previously in detail (Spanagel et al., 1996). After a seven-day period of acclimation, 30 rats were divided

Results

As presented in Fig. 1A, systolic blood pressure did not exhibit significant changes in both “control” and “ethanol” groups during 9 days of observation, while in rats from “withdrawal” group, arterial pressure rose by 21 mm Hg within 48 h of replacement of 20% ethanol with water.

Levels of renal excretion of MBG, endogenous ouabain and sodium, and hematocrit assessed at day 9 of the experiment are illustrated in Fig. 1B–E. Forced ethanol ingestion did not significantly affect any of the

Discussion

The main observation of the present experiment is that in rats, acute ethanol withdrawal is associated with a rise in arterial pressure, with renal sodium retention, volume expansion, and a drop in hematocrit, and with an increase in renal excretion of MBG, an endogenous bufadienolide with natriuretic, vasopressor and anti-addictive properties.

The fact that, in a subset of rats, withdrawal-induced pressor response was prevented by in vivo administration of anti-MBG antibody, indicates that MBG

Role of funding source

The experiments described in this paper were supported by the National Institute on Aging, National Institutes of Health Intramural Research Program and by Russian Foundation for Fundamental Science (grant 06-04-48956).

Contributors

Drs. AY Bagrov, Zvartau, and YY Bagrov designed the study. Drs. AY Bagrov, OV Fedorova and VA Kashkin wrote the protocol. Drs. AY Bagrov, OV Fedorova, and EG Lakatta managed the literature searches and analyses. Drs. Kashkin and Fedorova, and AY Bagrov performed the experiments and undertook the statistical analysis. Drs. AY Bagrov and VA Kashkin wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.

Conflict of interest

All the authors do not have any conflicts of interest.

Acknowledgements

The authors gratefully acknowledge excellent editorial assistance by Marinella Macri, and excellent technical support by Chad Boily BA, and Danielle Joseph, AA.

References (16)

There are more references available in the full text version of this article.

Cited by (7)

  • Alcohol Dependence, Withdrawal, and Relapse

    2014, Neurobiology of Alcohol Dependence
  • Neurochemical mechanisms of alcohol withdrawal

    2014, Handbook of Clinical Neurology
    Citation Excerpt :

    These include tachycardia, increased blood pressure, diaphoresis (heavy sweating), body temperature dysregulation, and gastrointestinal disturbances (nausea, vomiting). Animal models have demonstrated many of these classic sympathomimetic withdrawal symptoms, including altered cardiovascular function (Kashkin et al., 2008; Shirafuji et al., 2010), central and behavioral thermal dysregulation (Crawshaw et al., 1994), and gastrointestinal-related symptoms, such as diarrhea and reduced food and water intake (Friedman, 1980; Kliethermes, 2005). Most of these symptoms resolve within the acute phase of withdrawal.

  • New Insights into the Regulation of Na <sup>+</sup> ,K <sup>+</sup> -ATPase by Ouabain

    2012, International Review of Cell and Molecular Biology
    Citation Excerpt :

    Thus, limiting the list of conditions in which endogenous cardiotonic steroids may play a role, due to altered regulation of Na+,K+-ATPase, to the above mentioned is unrealistic. Although not addressed in this review, data indicate that these molecules are also implicated in several other conditions such as preeclampsia, depressive disorders, diabetes mellitus, ethanol addiction, and abnormal behavior (Bagrov et al., 2005; Brocardo et al., 2010; Goldstein et al., 2006, 2011; Kashkin et al., 2008; Nikitina et al., 2011; Schaefer et al., 2011). Na+,K+-ATPase is not simply an ion transporter but also functions as a signal transducer in response to cardiotonic steroid binding to its α-subunit.

  • Impairment of Na/K-ATPase signaling in renal proximal tubule contributes to Dahl salt-sensitive hypertension

    2011, Journal of Biological Chemistry
    Citation Excerpt :

    Second, these data suggest that CTS may induce increases in renal sodium excretion by multiple mechanisms. Specifically, these agents may increase vascular resistance as others have demonstrated (33–35) while also working through the renal mechanism discussed above. Although other hormonal systems no doubt interact with both of these pathways, such as the opposite effect of atrial natriuretic peptides on MBG-induced regulation of Na/K-ATPase activity in renal medulla and aortic rings (36), it does appear that the vascular mechanism is much more intact in the Dahl S rats suggesting that the molecular mechanisms of CTS signaling might be different in these different tissues.

View all citing articles on Scopus
View full text