Ovariectomy Exacerbates Acute Ethanol-Induced Tachycardia: Role of Nitric Oxide and NMDA Receptors in the Rostral Ventrolateral Medulla

Ethanol consumption influences cardiovascular functions. In humans, acute consumption of ethanol causes dose-dependent tachycardia. Our previous study showed that ethanol-induced tachycardia might involve decreased nitric oxide (NO) signaling in the brain’s medulla. NMDA receptors, another important target of ethanol, are one of the upstream signals of nitric oxide. Reports showed the modulation of NMDA receptor function by estrogen or estrogen receptors. The present study aims to examine the hypothesis that depletion of estrogen by ovariectomy (OVX) might modulate ethanol-induced tachycardia by regulating NMDA receptor function and NO signaling in the cardiovascular regulatory nucleus of the brain. Ethanol (3.2 g/kg, 40% v/v, 10 mL/kg) or saline (10 mL/kg) was administered by oral gavage in sham or OVX female Sprague-Dawley (SD) rats. The blood pressure (BP) and heart rate (HR) were measured using the tail-cuff method. The levels of phosphoserine 896 of the GluN1 subunit (pGluN1-serine 896) and NMDA GluN1 subunits (GluN1) were determined by immunohistochemistry. The expressions of nitric oxide synthase (NOS) and estrogen receptors in the tissue were measured by Western blotting. Nitric oxide contents were measured as total nitrate-nitrite by colorimetric assay kit. In a 2-h observation, there was no significant change in BP between the saline and ethanol groups. However, compared with saline, ethanol caused an increase in HR (tachycardia) in sham control or OVX rats. Interestingly, ethanol produced more significant tachycardia in the OVX group than in the sham control group. Nitric oxide levels were lower in the area of the rostral ventrolateral medulla (RVLM) 60 min following ethanol administration in OVX compared with sham control, without significant changes in the expression of NOS and estrogen receptors (ERα and ERβ). In addition, a decrease in the immunoreactivity of pGluN1-serine 896, without significant changes in GluN1, was found in neurons of RVLM 40 min following ethanol administration in OVX compared with sham control. Our results suggest that depletion of estradiol (E2) by OVX might exacerbate the tachycardia following ethanol administration, the underlying mechanism of which might be associated with decreased NMDA receptor function and NO level in the RVLM.

Aldehyde Dehydrogenase Inhibition Ameliorates Cardiac Dysfunction and Exacerbates Hypotension Caused by Alcohol in Female Rats

BACKGROUND

Aldehyde dehydrogenase 2 (ALDH2) protects against alcohol-evoked cardiac dysfunction in male rodents, but its role in the estrogen (E2 )-dependent hypersensitivity of female rats to alcohol-evoked myocardial oxidative stress and dysfunction is not known.

METHODS

We addressed this question by studying the effect of cyanamide (ALDH2 inhibitor) on cardiac function, blood pressure, alcohol-metabolizing enzyme (alcohol dehydrogenase, cytochrome P450 2E1, catalase, and ALDH2) activities, and cardiac redox status (reactive oxygen species, ROS; malondialdehyde, MDA) in the absence or presence of ethanol (EtOH) in female sham-operated (SO) and ovariectomized (OVX) rats.

RESULTS

Cyanamide attenuated the EtOH-evoked myocardial dysfunction (reduced dP/dtmax and LVDP) in SO rats. EtOH, cyanamide, or their combination did not alter dP/dtmax or LVDP in OVX rats. Cyanamide induced cardiac oxidative stress and abrogated the subsequent alcohol-evoked increases in ROS and MDA levels in SO rats. Neither EtOH nor cyanamide influenced ROS or MDA levels in OVX rats. Importantly, cyanamide exaggerated EtOH-evoked hypotension in SO and uncovered this hypotensive response in OVX rats, which implicates ALDH2 in the vasodilating effect of EtOH.

CONCLUSIONS

Contrary to our hypothesis, cyanamide attenuated the E2 -dependent cardiac dysfunction caused by alcohol, likely by preconditioning the heart to oxidative stress, while exacerbating the vasodilating effect of alcohol. The latter might predispose to syncope when cyanamide and alcohol are combined in females.

Role of Alcohol Oxidative Metabolism in Its Cardiovascular and Autonomic Effects

Several review articles have been published on the neurobehavioral actions of acetaldehyde and other ethanol metabolites as well as in major alcohol-related disorders such as cancer and liver and lung disease. However, very few reviews dealt with the role of alcohol metabolism in the adverse cardiac and autonomic effects of alcohol and their potential underlying mechanisms, particularly in vulnerable populations. In this chapter, following a brief overview of the dose-related favorable and adverse cardiovascular effects of alcohol, we discuss the role of ethanol metabolism in its adverse effects in the brainstem and heart. Notably, current knowledge dismisses a major role for acetaldehyde in the adverse autonomic and cardiac effects of alcohol because of its low tissue level in vivo. Contrary to these findings in men and male rodents, women and hypertensive individuals are more sensitive to the adverse cardiac effects of similar amounts of alcohol. To understand this discrepancy, we discuss the autonomic and cardiac effects of alcohol and its metabolite acetaldehyde in a model of hypertension, the spontaneously hypertensive rat (SHR) and female rats. We present evidence that enhanced catalase activity, which contributes to cardioprotection in hypertension (compensatory) and in the presence of estrogen (inherent), becomes detrimental due to catalase catalysis of alcohol metabolism to acetaldehyde. Noteworthy, studies in SHRs and in estrogen deprived or replete normotensive rats implicate acetaldehyde in triggering oxidative stress in autonomic nuclei and the heart via (i) the Akt/extracellular signal-regulated kinases (ERK)/nitric oxide synthase (NOS) cascade and (ii) estrogen receptor-alpha (ERα) mediation of the higher catalase activity, which generates higher ethanol-derived acetaldehyde in female heart. The latter is supported by the ability of ERα blockade or catalase inhibition to attenuate alcohol-evoked myocardial oxidative stress and dysfunction. More mechanistic studies are needed to further understand the mechanisms of this public health problem.

Role of neuronal nitric oxide synthase (nNOS) at medulla in tachycardia induced by repeated administration of ethanol in conscious rats

Background

Intake of ethanol (alcohol) has been shown to influence cardiovascular function; the underlying brain mechanism remains unclear. Noting that nitric oxide (NO) system in the CNS is involved in the regulation of cardiovascular function, the present study examined the role of NO in medulla in ethanol-induced cardiovascular changes.

Methods

Ethanol was administered by oral gavage at dose of 3.2 g/kg once every day for 8 consecutive days. Changes in blood pressure (BP) and heart rate (HR) in response to ethanol were measured by radiotelemetry method in freely moving female Sprague-Dawley rats. NO modulators were applied by intracerebroventricular (ICV) injection. The protein levels of nitric oxide synthase (NOS) and NO content in rostroventral medulla were measured by Western blot and nitrate/nitrite colorimetric assay kit, respectively.

Results

Ethanol intake had little effects on basal BP and HR following 8 consecutive day treatments. A significant increase in HR but not BP following ethanol intake was observed at 6th and 8th, but not at 1st and 4th day treatments as compared with saline group. A decrease in the protein expression of neuronal NOS (nNOS) but not inducible NOS or endothelial NOS and a decline in the level of NO in the medulla 30 min after ethanol administration was observed at 8th day treatment. ICV treatment with NO donors attenuated ethanol-induced tachycardia effects at 8th day treatment. Ethanol produced significantly tachycardia responses when ICV nNOS inhibitors were given at 1st day treatment.

Conclusion

Our results suggest that medulla nNOS/NO pathways play an important role in ethanol regulation of HR.

Estrogen Receptors α and β Play Major Roles in Ethanol-Evoked Myocardial Oxidative Stress and Dysfunction in Conscious Ovariectomized Rats

BACKGROUND

We documented the dependence of ethanol (EtOH)-evoked myocardial dysfunction on estrogen (E₂ ), and our recent estrogen receptor (ER) blockade study, in proestrus rats, implicated ERα signaling in this phenomenon. However, a limitation of selective pharmacological loss-of-function approach is the potential contribution of the other 2 ERs to the observed effects because crosstalk exists between the 3 ERs. Here, we adopted a "regain"-of-function approach (using selective ER subtype agonists) to identify the ER subtype(s) required for unraveling the E₂ -dependent myocardial oxidative stress/dysfunction caused by EtOH in conscious ovariectomized (OVX) rats.

METHODS

OVX rats received a selective ERα (PPT), ERβ (DPN), or GPER (G1) agonist (10 μg/kg; i.v.) or vehicle 30 minutes before EtOH (1.0 g/kg; infused i.v. over 30 minutes) or saline, and the hemodynamic recording continued for additional 60 minutes. Thereafter, left ventricular tissue was collected for conducting ex vivo molecular/biochemical studies.

RESULTS

EtOH had no hemodynamic effects in OVX rats, but reduced the left ventricular contractility index, dP/dt_max , and MAP after acute ERα (PPT) or ERβ (DPN) activation. These responses were associated with increases in the phosphorylation of ERK1/2 and eNOS, and in reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the myocardium. GPER activation (G1) only unraveled a modest EtOH-evoked hypotension and elevation in myocardial ROS. PPT enhanced catalase, DPN reduced ALDH2, while G1 had no effect on the activity of either enzyme, and none of the agonists influenced alcohol dehydrogenase or CYP2E1 activities in the myocardium. Blood EtOH concentration (96.0 mg/dl) was significantly reduced following ERα (59.8 mg/dl) or ERβ (62.9 mg/dl), but not GPER (100.3 mg/dl), activation in EtOH-treated OVX rats.

CONCLUSIONS

ERα and ERβ play major roles in the E₂ -dependent myocardial dysfunction caused by EtOH by promoting combined accumulation of cardiotoxic (ROS and MDA) and cardiodepressant (NOS-derived NO) molecules in female myocardium.

Estrogen modulation of the ethanol-evoked myocardial oxidative stress and dysfunction via DAPK3/Akt/ERK activation in male rats

Evidence suggests that male rats are protected against the hypotensive and myocardial depressant effects of ethanol compared with females. We investigated whether E2 modifies the myocardial and oxidative effects of ethanol in male rats. Conscious male rats received ethanol (0.5, 1 or 1.5g/kg i.v.) 30-min after E2 (1μg/kg i.v.) or its vehicle (saline), and hearts were collected at the conclusion of hemodynamic measurements for ex vivo molecular studies. Ethanol had no effect in vehicle-treated rats, but it caused dose-related reductions in LV developed pressure (LVDP), end-diastolic pressure (LVEDP), rate of rise in LV pressure (dP/dtmax) and systolic (SBP) and diastolic (DBP) blood pressures in E2-pretreated rats. These effects were associated with elevated (i) indices of reactive oxygen species (ROS), (ii) malondialdehyde (MDA) protein adducts, and (iii) phosphorylated death-associated protein kinase-3 (DAPK3), Akt, and extracellular signal-regulated kinases (ERK1/2). Enhanced myocardial anti-oxidant enzymes (heme oxygenase-1, catalase and aldehyde dehydrogenase 2) activities were also demonstrated. In conclusion, E2 promotes ethanol-evoked myocardial oxidative stress and dysfunction in male rats. The present findings highlight the risk of developing myocardial dysfunction in men who consume alcohol while receiving E2 for specific medical conditions.

Oxidative stress and autonomic dysregulation contribute to the acute time-dependent myocardial depressant effect of ethanol in conscious female rats

BACKGROUND

The molecular mechanisms of the acute hypotensive and indirectly assessed cardiac depressant effect of ethanol (EtOH)-evoked myocardial depression and hypotension in female rats are not known. We tested the hypothesis that a time-dependent myocardial depression caused by EtOH is initiated by its direct and indirect (cardiac vagal dominance) effects and is exacerbated by gradual development of oxidative stress.

METHODS

In conscious female rats, we directly measured left ventricular developed pressure (LVDP), the maximal rise of ventricular pressure over time (dP/dtmax ), blood pressure (BP), heart rate (HR), and sympathovagal activity following intragastric EtOH (1 g/kg) or water over 90 minutes. Catalytic activity of acetaldehyde (ACA)-generating (alcohol dehydrogenase [ADH] and catalase) and eliminating aldehyde dehydrogenase [ALDH2] enzymes along with mediators of oxidative stress were measured in myocardial tissues collected at 30, 60, or 90 minutes after EtOH or water.

RESULTS

EtOH reduced myocardial function (LVDP and dP/dtmax ) within 5 to 10 minutes before the steady fall in BP in conscious proestrus rats. Further, EtOH shifted the sympathovagal balance, analyzed by spectral analysis of high frequency and low frequency of interbeat intervals, toward vagal dominance. Prior vagal blockade (atropine) or antioxidant (tempol) treatment attenuated EtOH-evoked myocardial depression and hypotension. Ex vivo studies revealed time-dependent: (i) enhancement of ADH, but not ALDH2 activity (indicative of elevated ACA levels), (ii) increases in phosphorylated Akt and ERK1/2, NADPH-oxidase activity, reactive oxygen species, malondialdehyde, and 4-hydroxy-2-nonenal-modified proteins. These molecular responses along with reduced myocardial catalase activity were most evident at 90 minutes post-EtOH when the reductions in cardiac function and BP reached their nadir.

CONCLUSIONS

Vagal dominance and time-dependent myocardial oxidative stress along with the accumulation of cardiotoxic aldehydes mediate EtOH-evoked myocardial dysfunction and hypotension in conscious proestrus female rats.

PI3K/Akt-independent NOS/HO activation accounts for the facilitatory effect of nicotine on acetylcholine renal vasodilations: modulation by ovarian hormones

We investigated the effect of chronic nicotine on cholinergically-mediated renal vasodilations in female rats and its modulation by the nitric oxide synthase (NOS)/heme oxygenase (HO) pathways. Dose-vasodilatory response curves of acetylcholine (0.01–2.43 nmol) were established in isolated phenylephrine-preconstricted perfused kidneys obtained from rats treated with or without nicotine (0.5–4.0 mg/kg/day, 2 weeks). Acetylcholine vasodilations were potentiated by low nicotine doses (0.5 and 1 mg/kg/day) in contrast to no effect for higher doses (2 and 4 mg/kg/day). The facilitatory effect of nicotine was acetylcholine specific because it was not observed with other vasodilators such as 5′-N-ethylcarboxamidoadenosine (NECA, adenosine receptor agonist) or papaverine. Increases in NOS and HO-1 activities appear to mediate the nicotine-evoked enhancement of acetylcholine vasodilation because the latter was compromised after pharmacologic inhibition of NOS (L-NAME) or HO-1 (zinc protoporphyrin, ZnPP). The renal protein expression of phosphorylated Akt was not affected by nicotine. We also show that the presence of the two ovarian hormones is necessary for the nicotine augmentation of acetylcholine vasodilations to manifest because nicotine facilitation was lost in kidneys of ovariectomized (OVX) and restored after combined, but not individual, supplementation with medroxyprogesterone acetate (MPA) and estrogen (E2). Together, the data suggests that chronic nicotine potentiates acetylcholine renal vasodilation in female rats via, at least partly, Akt-independent HO-1 upregulation. The facilitatory effect of nicotine is dose dependent and requires the presence of the two ovarian hormones.

Nongenomic effects of estrogen mediate the dose-related myocardial oxidative stress and dysfunction caused by acute ethanol in female rats

Acute ethanol lowers blood pressure (BP) and cardiac output in proestrus and after chronic estrogen (E2) replacement in ovariectomized (OVX) female rats. However, whether rapid nongenomic effects of estrogen mediate these hemodynamic effects of ethanol remains unanswered. To test this hypothesis, we investigated the effect of ethanol (0.5 or 1.5 g/kg iv) on left ventricular (LV) function and oxidative markers in OVX rats pretreated 30 min earlier with 1 μg/kg E2 (OVXE2) or vehicle (OVX) and in proestrus sham-operated (SO) rats. In SO rats, ethanol caused significant and dose-related reductions in BP, rate of rise in LV pressure (LV dP/dtmax), and LV developed pressure (LVDP). These effects of ethanol disappeared in OVX rats and were restored in OVXE2 rats, suggesting rapid estrogen receptor signaling mediates the detrimental effects of ethanol on LV function. Ex vivo studies revealed that the estrogen-dependent myocardial dysfunction caused by ethanol was coupled with higher LV 1) generation of reactive oxygen species (ROS), 2) expression of malondialdehyde and 4-hydroxynonenal protein adducts, 3) phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinases (ERK1/2), and 4) catalase activity. ERK1/2 inhibition by PD-98059 (1 mg/kg iv) abrogated the myocardial dysfunction, hypotension, and the elevation in myocardial ROS generation caused by ethanol. We conclude that rapid estrogen receptor signaling is implicated in cellular events that lead to the generation of aldehyde protein adducts and Akt/ERK1/2 phosphorylation, which ultimately mediate the estrogen-dependent LV oxidative stress and dysfunction caused by ethanol in female rats.

Role of rostral ventrolateral medullary ERK/JNK/p38 MAPK signaling in the pressor effects of ethanol and its oxidative product acetaldehyde

BACKGROUND

We tested the hypothesis that alterations of the phosphorylation/dephosphorylation profile of mitogen-activated protein kinases (MAPKs) in the rostral ventrolateral medulla (RVLM) underlie the pressor response elicited by ethanol (EtOH) microinjection into the RVLM of spontaneously hypertensive rats (SHRs). The studies were extended to determine whether acetaldehyde (ACA), the primary oxidative product of EtOH, replicates the molecular effects of EtOH within the RVLM and the consequent pressor response.

METHODS

Effects of EtOH or ACA on blood pressure (BP) were evaluated in the absence or presence of selective JNK (SP600125), ERK (PD98059), p38 (SB203580), or ser/thr phosphatases (okadaic acid [OKA]) inhibitor.

RESULTS

Intra-RVLM EtOH (10 μg/rat) or ACA (2 μg/rat) caused a similar ERK2-dependent pressor response because EtOH or ACA-evoked increases in BP and in RVLM p-ERK2 level were abolished after pharmacologic inhibition of ERK phosphorylation. SP600125 abrogated the pressor action of EtOH, but not ACA, thus implicating JNK in EtOH action on BP. Despite EtOH enhancement of p38 phosphorylation, pharmacological studies argued against a causal role for this kinase in EtOH-evoked pressor response. RVLM phosphatase catalytic activity was not influenced by EtOH or ACA. Interestingly, pharmacologic phosphatase inhibition (OKA), which increased RVLM p-ERK2 and BP, abrogated the pressor effect of subsequently administered EtOH or ACA.

CONCLUSIONS

Enhancement of RVLM ERK2 phosphorylation constitutes a major molecular mechanism for the pressor response elicited by intra-RVLM EtOH or its metabolite, ACA, in conscious SHRs. Further, RVLM kinases dephosphorylation does not contribute to intra-RVLM EtOH- or ACA-evoked pressor response.

Differential modulation by vascular nitric oxide synthases of the ethanol-evoked hypotension and autonomic dysfunction in female rats

We recently reported that chronic exposure to ethanol lowers blood pressure (BP) via altering cardiac contractility and autonomic control in female rats. In this investigation we conducted pharmacological and molecular studies to elucidate the role of constitutive and inducible nitric oxide synthase (NOS) in these hemodynamic effects of ethanol. Changes caused by selective inhibition of eNOS [N(5)-(1-iminoethyl)-l-ornithine; l-NIO], nNOS (N(ω)-propyl-l-arginine; NPLA), or iNOS (1400W) in BP, heart rate (HR), myocardial contractility index (dP/dt(max)), and power spectral indices of hemodynamic variability were evaluated in telemetered female rats receiving ethanol (5%, w/v) or control liquid diet for 8 weeks. Ethanol increased plasma nitrite/nitrate (NOx) and enhanced the phosphorylation of eNOS and nNOS, but not iNOS, in the tail artery. Ethanol also reduced BP, +dP/dt(max), low-frequency bands of interbeat intervals (IBI(LF), 0.25-0.75 Hz) and IBI(LF/HF) ratio while high-frequency bands (IBI(HF), 0.75-3 Hz) were increased, suggesting parasympathetic overactivity. l-NIO (20 mg/kg i.p.) caused greater increases in BP in control than in ethanol-fed rats but elicited similar reductions in IBI(LF/HF) and +dP/dt(max) both groups. NPLA (1 mg/kg i.p.) caused minimal effects in control rats but exacerbated the reductions in BP, +dP/dt(max), and IBI(LF/HF) in ethanol-fed rats. No hemodynamic modifications were caused by 1400W (5 mg/kg i.p.) in either rat group. Together, these findings suggest that nNOS acts tonically to offset the detrimental cardiovascular actions of ethanol in female rats, and the enhanced vascular NO bioavailability may explain the blunted l-NIO evoked pressor response in ethanol-fed rats.

Enhanced catabolism to acetaldehyde in rostral ventrolateral medullary neurons accounts for the pressor effect of ethanol in spontaneously hypertensive rats

We have previously shown that ethanol microinjection into the rostral ventrolateral medulla (RVLM) elicits sympathoexcitation and hypertension in conscious spontaneously hypertensive rats (SHRs) but not in Wistar-Kyoto (WKY) rats. In this study, evidence was sought to implicate the oxidative breakdown of ethanol in this strain-dependent hypertensive action of ethanol. Biochemical experiments revealed significantly higher catalase activity and similar aldehyde dehydrogenase (ALDH) activity in the RVLM of SHRs compared with WKY rats. We also investigated the influence of pharmacological inhibition of catalase (3-aminotriazole) or ALDH (cyanamide) on the cardiovascular effects of intra-RVLM ethanol or its metabolic product acetaldehyde in conscious rats. Compared with vehicle, ethanol (10 μg/rat) elicited a significant increase in blood pressure in SHRs that lasted for the 60-min observation period but had no effect on blood pressure in WKY rats. The first oxidation product, acetaldehyde, played a critical role in ethanol-evoked hypertension because 1) catalase inhibition (3-aminotriazole treatment) virtually abolished the ethanol-evoked pressor response in SHRs, 2) intra-RVLM acetaldehyde (2 μg/rat) reproduced the strain-dependent hypertensive effect of intra-RVLM ethanol, and 3) ALDH inhibition (cyanamide treatment) uncovered a pressor response to intra-RVLM acetaldehyde in WKY rats similar to the response observed in SHRs. These findings support the hypothesis that local production of acetaldehyde, due to enhanced catalase activity, in the RVLM mediates the ethanol-evoked pressor response in SHRs.

Exacerbation of myocardial dysfunction and autonomic imbalance contributes to the estrogen-dependent chronic hypotensive effect of ethanol in female rats

Our previous studies showed that the hypotensive effect of chronic ethanol in female rats is reduced by ovariectomy (OVX) rats and was restored after estrogen replacement (OVXE(2)). Further, in randomly cycling rats, chronic ethanol increased cardiac parasympathetic dominance and subsequently reduced myocardial contractility and blood pressure (BP). In this study, we tested the hypothesis that alterations in myocardial contractility and sympathovagal control account for the E(2) exacerbation of the hemodynamic effects of ethanol. BP, myocardial contractility (+dP/dt(max)), and spectral cardiovascular autonomic profiles were evaluated in radiotelemetered OVX, and OVXE(2) rats receiving liquid diet with or without ethanol (5%, w/v) for 13 weeks. In OVX rats, ethanol caused modest hypotension along with significant increases in +dP/dt(max) during weeks 2-5. The high-frequency (IBI(HF), 0.75-3 Hz) and low-frequency (IBI(LF), 0.25-0.75 Hz) bands of interbeat intervals were briefly increased and decreased, respectively, by ethanol. Compared with its effects in OVX rats, chronic treatment of OVXE(2) rats with ethanol elicited significantly greater and more sustained reductions in systolic (SBP) and diastolic (DBP) blood pressures and +dP/dt(max). Altered sympathovagal balance and parasympathetic overactivity were more evident in ethanol-treated OVXE(2) rats as suggested by the sustained: (i) increases in high-frequency bands of interbeat intervals (IBI(HF), 0.75-3 Hz), and (ii) decreases in low-frequency IBI bands (IBI(LF), 0.25-0.75 Hz), IBI(LF/HF) ratio and +dP/dt(max). The plasma ethanol concentration was not affected by changes in the hormonal milieu. These findings suggest that estrogen exacerbates the ethanol-evoked reductions in myocardial contractility and BP and the associated parasympathetic overactivity in female rats.

Estrogen dependence of the renal vasodilatory effect of nicotine in rats: role of α7 nicotinic cholinergic receptor/eNOS signaling

AIMS

We recently reported that acute exposure to nicotine vasodilates the renal vasculature of male rats via facilitation of endothelial nitric oxide synthase (eNOS). In this study, we investigated whether this effect of nicotine is sexually dimorphic and the role of estrogen in modulating the nicotine effect.

MAIN METHODS

Nicotine-evoked vasodilation was evaluated in phenylephrine-preconstricted perfused kidneys obtained from male, proestrus female, ovariectomized (OVX) and estrogen-replaced OVX (OVXE(2)) rats.

KEY FINDINGS

Nicotine infusion (5×10(-5), 1×10(-4), and 5×10(-4) M) produced greater concentration-dependent reductions in the renal perfusion pressure (RPP) in an isolated kidney from proestrus females than from males. Inhibition of NOS by N(G)-nitro-L-arginine abolished the nicotine-evoked reduction in RPP and abolished the gender difference in the nicotine effect. Nicotine vasodilation was also attenuated in kidneys isolated from OVX and diestrus rats, models characterized by reduced estrogen levels. Further, estrogen or L-arginine supplementation in OVX rats largely restored the renal vasodilatory response to nicotine. Estrogen receptor blockade by tamoxifen abrogated the enhanced nicotine-evoked vasodilation elicited by E(2) in OVX rats. The nitrite/nitrate levels and protein expressions of eNOS and α(7) nicotinic cholinergic receptor (α(7) nAChRs) were significantly higher in renal tissues of OVXE(2) compared with OVX rats, suggesting a facilitatory effect for E(2) on α(7) nAChRs/eNOS signaling.

SIGNIFICANCE

Estrogen-dependent facilitation of NOS signaling mediates the enhanced vasodilator capacity of nicotine in the renal vasculature of female rats. Preliminary evidence also suggests a potential role for α(7) nAChRs in this estrogen-dependent phenomenon.

Upregulation of cardiac NOS due to endotoxemia and vagal overactivity contributes to the hypotensive effect of chronic ethanol in female rats

We previously reported that chronic ethanol lowers blood pressure in female rats. In this study, hemodynamic, biochemical, and immunoblot analyses were performed to investigate: (i) the roles of cardiac contractility and autonomic activity in the hypotensive action of ethanol, and (ii) whether endotoxemia-induced upregulation of cardiac and/or vascular nitric oxide synthase (NOS) isoforms underlies the hypotensive and cardiac effects of ethanol. Telemetric monitoring of blood pressure, heart rate, and myocardial contractility (dP/dt(max)) was performed in female rats receiving liquid diet with or without ethanol (5% w/v, 13weeks). Autonomic control was assessed by frequency domain analysis of interbeat intervals (IBI) and systolic blood pressure (SBP). Compared with pair-fed controls, ethanol caused sustained reductions in blood pressure, heart rate, and+dP/dt(max). Ethanol feeding increased the spectral power of high-frequency band (IBI(HF), 0.75-3Hz) and decreased the low-frequency band (IBI(LF), 0.25-0.75Hz) and IBI(LF/HF) ratio, suggesting increased cardiac parasympathetic dominance. In contrast, vascular tone was not affected by ethanol because SBP spectral bands and plasma norepinephrine remained unchanged. Myocardial expressions of eNOS and its upstream regulators, phosphatidylinositol 3-kinase (PI3K) and Akt, and plasma endotoxin and nitrite/nitrate were increased by ethanol. Myocardial iNOS was also increased by ethanol whereas nNOS remained unchanged and aortic levels of all NOS isoforms were not altered by ethanol. These findings suggest that facilitation of myocardial PI3K/Akt/eNOS and iNOS pathways, due possibly to ethanol-induced endotoxemia and/or increased cardiac parasympathetic dominance, might constitute a cellular mechanism for the reduced myocardial contractility and hypotension caused by ethanol in female rats.

Sex and hormonal influences on the nicotine-induced attenuation of isoprenaline vasodilations in the perfused rat kidney

We previously reported that nicotine impairs betta-adrenoceptor-mediated renovascular control in male rats. Here, we investigated the roles of sex and estrogen in nicotine-betta-adrenoceptor renal interaction. The effect of nicotine on renal vasodilations caused by isoprenaline was evaluated in phenylephrine-preconstricted perfused kidneys of male and proestrus female rats in absence and presence of NG-nitro-<span class="smallcap">l</span>-arginine (<span class="smallcap">l</span>-NNA, a NOS inhibitor). The interaction was also studied in diestrus and ovariectomized (OVX) rats treated with or without estradiol, tamoxifen, or <span class="smallcap">l</span>-arginine. Bolus isoprenaline (0.03-8.0 micromol) elicited dose-dependent renal vasodilations; female preparations were more sensitive (smaller ED50) to isoprenaline-induced vasodilation than were male preparations. Infusion of nicotine (500 micromol/L) reduced isoprenaline vasodilations in the 2 sexes and abolished male-female differences in isoprenaline responses. <span class="smallcap">l</span>-NNA reduced isoprenaline vasodilations in proestrus but not in male preparations. Also, in the presence of <span class="smallcap">l</span>-NNA, nicotine caused no attenuation of isoprenaline vasodilations in proestrus preparations. Renal responses to isoprenaline together with the attenuation of these responses by nicotine were reduced by OVX and restored to near-proestrus levels after supplementation with estradiol, the estrogen receptor modulator tamoxifen, or <span class="smallcap">l</span>-arginine. In diestrus rats, which exhibited reduced plasma estradiol, nicotine caused less attenuation of isoprenaline vasodilations. We conclude that impairment of estrogen-NOS signaling constitutes a possible cellular mechanism for the detrimental effect of nicotine on isoprenaline vasodilations in female rats. The mechanism of the nicotine-induced attenuation of isoprenaline vasodilation in male kidneys, which is NOS-independent, remains to be elucidated.

Facilitation of central imidazoline I(1)-site/extracellular signal-regulated kinase/p38 mitogen-activated protein kinase signalling mediates the hypotensive effect of ethanol in rats with acute renal failure

BACKGROUND AND PURPOSE

This study investigated the role of central sympathetic activity and related mitogen-activated protein kinase (MAPK) signalling in the cardiovascular effects of ethanol in a model of acute renal failure (ARF).

EXPERIMENTAL APPROACH

The effects of pharmacological interventions that inhibit peripheral or central sympathetic activity or MAPK on the cardiovascular actions of ethanol in rats with ARF induced by glycerol were evaluated.

KEY RESULTS

Glycerol (50%, 10 mL.kg(-1), i.m.) caused progressive increases and decreases in blood pressure (BP) and heart rate (HR) respectively. Subsequent i.v. ethanol (0.25 or 1 g.kg(-1)) elicited dose-related changes in BP (decreases) and HR (increases). These effects were replicated after intracisternal (i.c.) administration of ethanol. Blockade of nicotinic cholinoceptors (nAChR, hexamethonium, 20 mg.kg(-1)) or alpha(1)-adrenoceptors (prazosin, 1 mg.kg(-1)) attenuated cardiovascular effects of ethanol. Ethanol hypotension was also attenuated after the centrally acting sympatholytic drug moxonidine (selective I(1)-site agonist, 100 microg.kg(-1) i.v.), but not guanabenz (selective alpha(2)-receptor agonist, 30 microg.kg(-1), i.v.), suggesting involvement of central circuits of I(1) sites in ethanol-evoked hypotension. Selective blockade I(1) sites (efaroxan) but not alpha(2) (yohimbine) adrenoceptors abolished the hypotensive response to ethanol. Intracisternal administration of PD98059 or SB203580, inhibitors of extracellular signal-regulated kinase (ERK 1/2) and p38 MAPK, respectively, reduced the hypotensive action of moxonidine or ethanol. When used simultaneously, the two MAPK inhibitors produced additive attenuation of ethanol hypotension.

CONCLUSIONS AND IMPLICATIONS

Sympathoinhibitory pathways of central I(1)-sites and downstream ERK/p38 MAPK signalling were involved in the hypotensive action of ethanol in ARF.

Facilitation of myocardial PI3K/Akt/nNOS signaling contributes to ethanol-evoked hypotension in female rats

BACKGROUND

The mechanism by which ethanol reduces cardiac output (CO) and blood pressure (BP) in female rats remains unclear. We tested the hypothesis that enhancement of myocardial phosphatidylinositol 3-kinase (PI3K)/Akt signaling and related neuronal nitric oxide synthase (nNOS) and/or endothelial nitric oxide synthase (eNOS) activity constitutes a cellular mechanism for the hemodynamic effects of ethanol.

METHODS

We measured the level of phosphorylated eNOS (p-eNOS) and p-nNOS in the myocardium of ethanol (1 g/kg intragastric, i.g.) treated female rats along with hemodynamic responses [BP, CO, stroke volume, (SV), total peripheral resistance, (TPR)], and myocardial nitrate/nitrite levels (NOx) levels. Further, we investigated the effect of selective pharmacological inhibition of nNOS with N(omega)-propyl-l-arginine (NPLA) or eNOS with N(5)-(1-iminoethyl)-l-ornithine (l-NIO) on cellular, hemodynamic, and biochemical effects of ethanol. The effects of PI3K inhibition by wortmannin on the cardiovascular actions of ethanol and myocardial Akt phosphorylation were also investigated.

RESULTS

The hemodynamic effects of ethanol (reductions in BP, CO, and SV) were associated with significant increases in myocardial NOx and myocardial p-nNOS and p-Akt expressions while myocardial p-eNOS remained unchanged. Prior nNOS inhibition by NPLA (2.5 or 12.5 microg/kg) attenuated hemodynamic effects of ethanol and abrogated associated increases in myocardial NOx and cardiac p-nNOS contents. The hemodynamic effects of ethanol and increases in myocardial p-Akt phosphorylation were reduced by wortmannin (15 microg/kg). On the other hand, although eNOS inhibition by l-NIO (4 or 20 mg/kg) in a dose-dependent manner attenuated ethanol-evoked hypotension, the concomitant reductions in CO and SV remained unaltered. Also, selective eNOS inhibition uncovered dramatic increases in TPR in response to ethanol, which appeared to have offset the reduction in CO. Neither NPLA nor l-NIO altered plasma ethanol levels.

CONCLUSIONS

These findings implicate the myocardial PI3K/Akt/nNOS signaling in the reductions in BP and CO produced by ethanol in female rats.

Estrogen-dependent enhancement of NO production in the nucleus tractus solitarius contributes to ethanol-induced hypotension in conscious female rats

BACKGROUND

Our previous pharmacological and cellular studies showed that peripheral (cardiac and vascular) nitric oxide synthase (NOS)-derived NO is implicated in the estrogen (E(2))-dependent hypotensive action of ethanol in female rats. The objective of this study was to test the hypothesis that enhanced NO production in the nucleus tractus solitarius (NTS) is implicated in the E(2)-dependent hypotensive action of ethanol.

METHODS

To achieve this goal, we utilized in vivo electrochemistry to measure real time changes in neuronal NO to investigate the acute effects of intragastric ethanol (0, 0.5, or 1 g/kg) on NO in NTS neurons, blood pressure (BP), and heart rate (HR) in conscious female rats in the absence (ovariectomized, OVX, rats) or presence of E(2).

RESULTS

In sham operated (SO) rats, ethanol elicited dose-related increase in NTS NO and reduction in BP. These neurochemical and BP effects of ethanol were absent in OVX rats. Whether the neurochemical effect of ethanol and the associated hypotension are dependent on rapid E(2) signaling was investigated. In OVX rats pretreated, 30 minutes earlier, with E(2) (1 microg/kg), intragastric ethanol (1 g/kg) increased NTS NO and reduced BP and these responses were comparable to those obtained in SO rats.

CONCLUSIONS

The present findings suggest that increased production of NO in NTS neurons contributes to ethanol-evoked hypotension in female rats. Further, ethanol enhancement of neuronal NO production in the brainstem is dependent on rapid E(2) signaling.

Influence of gender on the association of alcohol drinking with blood pressure

BACKGROUND

The purpose of this study was to determine whether gender influences the association of alcohol drinking with blood pressure.

METHODS

The subjects (43,810 healthy men and women at ages of 35-54 years) were divided into five groups by average daily ethanol intake (non-, very light (<10 g per day), light (> or =10 g and <20 g per day), moderate (> or =20 g and <30 g per day), and heavy (> or =30 g per day) drinkers). The means of each variable after adjustment for age, body weight, and history of smoking were compared among the groups.

RESULTS

Systolic blood pressure of men was significantly higher in moderate and heavy drinkers than in nondrinkers, and systolic blood pressure of women was significantly higher in heavy drinkers but not in moderate drinkers than in nondrinkers. Diastolic blood pressure of men and women was significantly higher in light, moderate and heavy drinkers than in nondrinkers. The differences in systolic and diastolic blood pressure between drinkers and nondrinkers were greater in men than in women. Both in men and women, serum HDL cholesterol was significantly higher in all four drinker groups than in the nondrinker group, and the difference between drinkers and nondrinkers was greater in women than in men. The above findings were not altered when age- and alcohol intake-matched groups of subjects were used.

CONCLUSIONS

The results suggest that blood pressure is more prone to be elevated by alcohol drinking in men than in women.

Gender-specific vascular effects elicited by chronic ethanol consumption in rats: a role for inducible nitric oxide synthase

BACKGROUND AND PURPOSE

Epidemiological data suggest that the risk of ethanol-associated cardiovascular disease is greater in men than in women. This study investigates the mechanisms underlying gender-specific vascular effects elicited by chronic ethanol consumption in rats.

EXPERIMENTAL APPROACH

Vascular reactivity experiments using standard muscle bath procedures were performed on isolated thoracic aortae from rats. mRNA and protein for inducible NO synthase (iNOS) and for endothelial NOS (eNOS) was assessed by RT-PCR or western blotting, respectively.

KEY RESULTS

In male rats, chronic ethanol consumption enhanced phenylephrine-induced contraction in both endothelium-intact and denuded aortic rings. However, in female rats, chronic ethanol consumption enhanced phenylephrine-induced contraction only in endothelium denuded aortic rings. After pre-incubation of endothelium-intact rings with L-NAME, both male and female ethanol-treated rats showed larger phenylephrine-induced contractions in aortic rings, compared to the control group. Acetylcholine-induced relaxation was not affected by ethanol consumption. The effects of ethanol on responses to phenylephrine were similar in ovariectomized (OVX) and intact (non-OVX) female rats. In the presence of aminoguanidine, but not 7-nitroindazole, the contractions to phenylephrine in rings from ethanol-treated female rats were greater than that found in control tissues in the presence of the inhibitors. mRNA levels for eNOS and iNOS were not altered by ethanol consumption. Ethanol intake reduced eNOS protein levels and increased iNOS protein levels in aorta from female rats.

CONCLUSIONS AND IMPLICATIONS

Gender differences in the vascular effects elicited by chronic ethanol consumption were not related to ovarian hormones but seemed to involve the upregulation of iNOS.

Endotoxemia-mediated induction of cardiac inducible nitric-oxide synthase expression accounts for the hypotensive effect of ethanol in female rats

We have recently shown that intragastric (i.g.) ethanol lowers blood pressure (BP) in conscious female rats via a reduction in cardiac output (CO). However, the mechanisms implicated in these hemodynamic effects of ethanol are not known. Therefore, we tested the hypothesis that ethanol-evoked endotoxemia mediates the reduction in CO via enhanced myocardial inducible nitric-oxide synthase (iNOS) expression. Immunoblot (myocardial iNOS), biochemical (plasma endotoxin and nitrite/nitrate), and integrative [BP, heart rate, CO, stroke volume (SV), and total peripheral resistance (TPR)] studies were conducted in conscious female rats that received i.g. ethanol (1 g/kg) in the absence or presence of 1400W (N-(3-[aminomethyl]benzyl) acetamidine) or ampicillin to selectively inhibit iNOS and to eliminate endogenous endotoxin, respectively. Ethanol-evoked hypotension coincided with reductions in CO and SV and increases in: 1) TPR, 2) plasma endotoxin and nitrite/nitrate, and 3) myocardial iNOS expression. These effects of ethanol were virtually abolished in rats pretreated with ampicillin (200 mg/kg/day for 2 days by gavage) or with 1400W (5 mg/kg i.p.) except for the increase in plasma endotoxin, which persisted in 1400W-pretreated rats. These findings yield insight into the mechanistic role of endotoxin-myocardial iNOS signaling in the cardiodepressant action of ethanol, which accounts for its hypotensive effect in conscious female rats.

Role of Myocardial Contractility and Autonomic Control in the Hypotensive Response to a Limited Access Ethanol Paradigm in SHRs

BACKGROUND

Previous experimental studies that evaluated the chronic hemodynamic effect of ethanol employed the continuous exposure protocol of ethanol, which does not mimic the pattern of alcohol consumption in humans. This study dealt with the long-term hemodynamic and cardiovascular autonomic effects of ethanol, in a limited-access regimen in telemetered spontaneously hypertensive rats (SHRs).

METHODS

Changes in blood pressure (BP), heart rate (HR), myocardial contractility (dP/dt(max)), and spectral cardiovascular autonomic profiles during the ethanol exposure period (2.5 or 5% w/v, 8 h/d, 8:30 am till 4:30 pm) were followed for 12 weeks.

RESULTS

Compared with control pair-fed SHRs, body weight and urine output, osmolality, and potassium levels were decreased in SHRs receiving 5% but not 2.5% ethanol. Blood pressure showed progressive falls during ethanol-feeding periods with a maximum effect observed at week 5. The peak hypotensive effect was maintained thereafter in SHRs receiving 5% ethanol in contrast to steady rises in BP in the 2.5% ethanol group to near-control levels by the conclusion of the study. Heart rate was slightly but significantly increased by ethanol 5% whereas dP/dt(max) showed persistent reductions. Power spectral analysis showed that ethanol attenuated the baroreflex gain of HR as suggested by the reductions in index alpha, the spectral index of spontaneous baroreflex sensitivity (BRS).

CONCLUSIONS

It is concluded that limited access ethanol drinking in SHRs elicited hypotension that was concentration dependent and mediated, at least partly, through reductions in myocardial contractility. Baroreflex sensitivity attenuation by ethanol appeared to have limited the tachycardic response to ethanol and perhaps its capacity to offset the evoked hypotension.

Alcohol consumption and blood pressure in the adult US population: assessment of gender-related effects

OBJECTIVE

Our objective was to assess the gender-related effects of alcohol consumption on blood pressure (BP) in a representative sample of the adult US population.

METHODS

We examined data from the National Health and Nutrition Examination Survey 1999-2000. The effects of various risk factors for hypertension on BP were examined with analysis of covariance statistics.

RESULTS

Of the 5448 adults over 20 years of age, 2650 (48.7%) reported the intake of one or more drinks per day over the past year. In this population, the mean +/- SEM age was 46.9 +/- 0.34 years, the body mass index was 24.8 kg/m, 1257 (47.4%) were women, systolic BP was 124.3 +/- 0.44 mmHg and diastolic BP was 72.7 +/- 0.27 mmHg. Hypertension was reported in 21.1%, diabetes in 5.1% and cigarette smoking in 39.7%. A significant effect on systolic BP was shown with age (P < 0.01), body mass index (P < 0.01), race (P = 0.01), gender (P < 0.01) and diabetes (P < 0.01). The interaction with gender and alcohol drinking level was significant (P = 0.02). Post-hoc analysis localized the source of this effect. There was a significant increase in systolic BP between one and three and between one and four, but not between one and two, drinks per day in men. This effect was not observed in women.

CONCLUSION

Consistent with previous reports, our study suggests that alcohol intake up to two drinks per day has no effect on BP. There was a gender-related effect of alcohol intake in excess of two drinks per day on BP, with increased BP observed only in men but not in women.

Upregulation of vascular inducible nitric oxide synthase mediates the hypotensive effect of ethanol in conscious female rats

Previous reports from our laboratory have shown that ethanol elicits hypotension in female but not in male rats and that this effect of ethanol is estrogen dependent (El-Mass MM and Abdel-Rahman AA. Alcohol Clin Exp Res 23: 624-632, 1999; El-Mass MM and Abdel-Rahman AA. Clin Exp Hypertens 21: 1429-1445, 1999). In the present study, we tested the hypothesis that ethanol lowers blood pressure in female rats via upregulation of the inducible nitric oxide synthase (iNOS) in vascular tissues. The effects of pretreatment with NG-nitro-L-arginine (NOARG; nonselective nitric oxide synthase inhibitor) or aminoguanidine (selective iNOS inhibitor) on hemodynamic responses elicited by intragastric (ig) ethanol were determined in conscious female rats. Changes in vascular (aortic) iNOS protein expression evoked by ethanol in the presence and absence of aminoguanidine were also measured by immunohistochemistry. Compared with control (water treated) female rats, ethanol (1 g/kg ig) elicited hypotension that was associated with a significant increase in the aortic iNOS activity. The hypotensive effect of ethanol was virtually abolished in rats infused with the nitric oxide synthase inhibitor NOARG, suggesting a role for nitric oxide in ethanol hypotension. The inability of ethanol to lower blood pressure in NOARG-treated rats cannot be attributed to the presence of elevated blood pressure in these rats because ethanol produced hypotension when blood pressure was raised to comparable levels with phenylephrine infusion. Selective inhibition of iNOS by aminoguanidine (45 mg/kg ip), which had no effect on baseline blood pressure, abolished both the hypotensive action of subsequently administered ethanol and the associated increases in aortic iNOS content. These findings implicate vascular iNOS, at least partly, in the acute hypotensive action of ethanol in female rats.

Role of endothelial adenosine receptor-mediated vasorelaxation in ethanol-induced hypotension in hypertensive rats

Our previous findings showed that chronic ethanol feeding lowers blood pressure in spontaneously hypertensive rats. The present study investigated the role of the adenosine receptor-endothelial nitric oxide (NO) pathway in the hypotensive response to ethanol. Changes in blood pressure were evaluated in radiotelemetered pair-fed rats receiving liquid diet with or without ethanol (2.5% or 5%, w/v) for 12 weeks. The vasorelaxant activity of the adenosine analogue 5'-N-ethylcarboxamidoadenosine (NECA) in isolated aortic rings obtained from ethanol and control rats were evaluated. Ethanol (2.5% and 5%) lowered blood pressure in a dose-dependent manner. The hypotension started at week 1, reached its maximum at week 4 and remained so thereafter. In aortas with intact endothelium, NECA (10(-10) to 10(-4) M) produced a concentration-dependent relaxation of the phenylephrine-precontracted aortas. Compared with control rats, ethanol (2.5% and 5%) caused significant and concentration-related increases in NECA responses. This effect of ethanol was attenuated by the adenosine receptor antagonist 8-sulfophenyltheophylline and the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA). Further, endothelium denudation abolished the ethanol-evoked enhancement of NECA responses. The vasorelaxant responses to acetylcholine or sodium nitroprusside in aortic rings were not influenced by ethanol. In conclusion, the present findings suggest that chronic ethanol enhances the NO-dependent vasorelaxant responses to adenosine receptor activation and this may explain, at least partly, the mechanism of the hypotensive effect of ethanol in spontaneously hypertensive rats.

An association between the estrogen-dependent hypotensive effect of ethanol and an elevated brainstem c-jun mRNA in female rats

We have recently demonstrated that chronic ethanol administration lowers blood pressure (BP) in female rats and this effect is significantly attenuated by ovariectomy. The present study investigated whether ethanol hypotension is estrogen dependent. Further, since estrogen regulates AP-1 activity, the study was extended to determine whether estrogen/c-jun interaction is involved in the estrogen-dependent hypotensive effect of ethanol. Changes in BP and heart rate (HR) were evaluated in radiotelemetered pair-fed sham-operated (SO), ovariectomized (OVX), and OVX estradiol (E2)-treated rats receiving liquid diet with or without ethanol (5%, w/v) for 12 weeks. The in situ hybridization technique was used to measure the c-jun mRNA expression in two brainstem areas, the nucleus tractus solitarius (NTS) and the rostral ventrolateral medulla (RVLM). Ethanol feeding caused significant (P<0.05) decreases in BP in SO rats that started at week 1 and reached its maximum (approximately 10 mmHg) at week 6 and remained at that level till the end of week 12. In OVX rats, ethanol had no effect on BP during the first 5 weeks after which a decrease of 5 mmHg was demonstrated and remained thereafter. Estrogen replacement (17beta-estradiol subcutaneous pellet, 14.2 microg/day) restored the hypotensive effect of ethanol to a level similar to that of SO rats both in terms of magnitude and duration. Densitometric analysis of the in situ hybridization autoradiograms revealed that OVX and E2 replacement had no effect on c-jun mRNA expression in the NTS or RVLM. Ethanol feeding produced a significant (twofold) increase in c-jun mRNA expression in the RVLM of SO rats versus no effect in the NTS. The increased expression of c-jun mRNA observed following ethanol treatment in the RVLM of SO rats was abolished in OVX rats and restored to SO levels after E2 replacement. These findings suggest a link between the estrogen-dependent hypotensive effect of chronically administered ethanol and the increased expression of c-jun mRNA in the brainstem of female rats.

Ovariectomy alters the chronic hemodynamic and sympathetic effects of ethanol in radiotelemetered female rats

This study determined the chronic hemodynamic effects of ethanol in telemetered freely moving female Sprague-Dawley rats. The role of ovarian hormones and sympathetic activity in the modulation of ethanol responses was also investigated. Changes in blood pressure (BP), heart rate (HR), and plasma estrogen and norepinephrine (NE, as index of sympathetic activity) were evaluated in pair-fed sham-operated (SO) and ovariectomized (OVX) rats receiving liquid diet with or without ethanol (5%, w/v) for 12 weeks. OVX caused a significant increase (about 40 g) in body weight, compared with the sham operation, which was apparent after two weeks and remained so for the duration of the study. The body weight showed gradual and similar increases in both ethanol and control groups. Ethanol feeding had no effect on the plasma estrogen level in SO or OVX rats. Daily ethanol intake was significantly (P < 0.05) less in OVX compared with SO rats whereas the blood ethanol concentration were similar in the two groups except for a significantly (P < 0.05) higher level in OVX rats at weeks 8, 10, and 11. Ethanol feeding caused significant (P < 0.05) decreases in BP in SO rats that started at week land reached maximal response (approximately 10 mmHg) at week 6 and remained at that level till the end of week 12. In OVX rats, ethanol had no effect on BPduring the first 5 weeks of the study. A slight but significant reduction in BP (about 5 mmHg) by ethanol in OVX rats started to appear at week 6 and remained for the following 5 weeks. The reduced hypotensive effect of ethanol in OVX rats was associated with an increase in the sympathetic activity as indicated by the significant (P < 0.05) increases in plasma NE levels. This sympathoexcitatory effect of ethanol was not demonstrated in SO rats. The HR was not affected by ethanol in the two groups of rats except for significant (P < 0.05) increases at weeks 1 through 3 in SO rats. The present findings suggest that the ovarian hormones modulate, at least partly, the hemodynamic and neurohumoral effects of chronic ethanol feeding in female rats. Ethanol lowers BP in female rats and this effect was delayed and diminished in OVX rats due possibly to the associated increase in sympathetic activity.