Gender difference in baroreflex-mediated bradycardia in young rats: role of cardiac sympathetic and parasympathetic components

1999 ◽  
Vol 77 (5) ◽  
pp. 358-366 ◽  
Author(s):  
Abdel A Abdel-Rahman
Keyword(s):  
Heart Rate ◽  
Sexual Dimorphism ◽  
Gender Difference ◽  
Baroreflex Sensitivity ◽  
Reciprocal Relationship ◽  
Female Rats ◽  
Male Rats ◽  
Beta Adrenergic ◽  
Conscious Rats ◽  
Young Rats

In a previous clinical study we have demonstrated a significantly lower baroreflex-mediated bradycardic response in young women compared with men. The present study determined whether sexual dimorphism in baroreflex sensitivity in young rats also covers the reflex tachycardic response. The study was then extended to test the hypothesis that an attenuated cardiac cholinergic component of the baroreflex heart rate response in females may account for the gender difference. Baroreflex sensitivity (BRS) was expressed as the regression coefficient of the reciprocal relationship between evoked changes in blood pressure and heart rate. BRS measured in conscious rats with phenylephrine (BRSPE) and nitroprusside (BRSNP) represented the reflex bradycardic and tachycardic responses, respectively. Female rats exhibited significantly lower BRSPE compared with male rats (-1.53 ± 0.1 vs. -2.36 ± 0.13 beats·min-1·mmHg-1; p < 0.05) but similar BRSNP (-2.60 ± 0.20 vs. -2.29 ± 0.17 beats·min-1·mmHg-1). Blockade of cardiac muscarinic receptors with atropine methyl bromide elicited greater attenuation of BRSPE in male than in female rats (72 ± 4.6 vs. 53 ± 6.7% inhibition; p < 0.01) and abolished the gender difference. In male rats cardiac muscarinic blockade attenuated BRSPE significantly more than did cardiac beta-adrenergic receptor blockade with propranolol (72 ± 4.6 vs. 43 ± 2.7; p < 0.01), which suggests greater dependence of BRSPE on the parasympathetic component. In females, muscarinic and beta-adrenergic blockade elicited similar attenuation of BRSPE. The findings suggest that (i) BRS is differentially influenced by gender; female rats exhibit substantially lower BRSPE but similar BRSNP compared with age-matched male rats and (ii) the sexual dimorphism in BRSPE results, at least partly, from a smaller increase in vagal outflow to the heart in response to baroreceptor activation.Key words: gender difference, baroreflex sensitivity, vagal outflow, conscious rats.

Estrogen enhances baroreflex control of heart rate in conscious ovariectomized rats

1998 ◽  
Vol 76 (4) ◽  
pp. 381-386 ◽  
Author(s):  
Mahmoud M El-Mas ◽  
Abdel A Abdel-Rahman
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Baroreflex Sensitivity ◽  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
Baroreflex Function ◽  
Vehicle Treatment

In previous studies, we have shown that the baroreflex control of heart rate is significantly attenuated in females compared with age-matched males. This study investigated the role of estrogen in the modulation of baroreflex function in conscious unrestrained rats. Baroreflex-mediated decreases in heart rate in response to increments in blood pressure evoked by phenylephrine were evaluated in conscious freely moving male and female Sprague-Dawley rats as well as in ovariectomized rats. The effect of a 2-day 17 beta -estradiol (50 µg ·kg-1 ·day-1, s.c.) or vehicle treatment on baroreflex sensitivity was investigated in ovariectomized rats. Intravenous bolus doses of phenylephrine (1-16 µg/kg) elicited dose-dependent pressor and bradycardic responses in all groups of rats. Regression analysis of the baroreflex curves relating increments in blood pressure to the associated heart rate responses revealed a significantly (p < 0.05) smaller baroreflex sensitivity in female compared with male rats (-1.22 ± 0.07 and -1.85 ± 0.15 beats ·min-1 ·mmHg-1, respectively), suggesting an attenuated baroreflex function in females. In age-matched ovariectomized rats, baroreflex sensitivity showed further reduction (-0.93 ± 0.02 beats ·min-1 ·mmHg-1). Treatment of ovariectomized rats with 17 beta -estradiol significantly (p < 0.05) enhanced the baroreflex sensitivity (-1.41 ± 0.16 beats ·min-1 ·mmHg-1) to a level that was slightly higher than that of sham-operated female rats. Furthermore, baroreflex sensitivity of ovariectomized estradiol-treated rats was not significantly different from that of age-matched male rats. The vehicle, on the other hand, had no effect on baroreflex sensitivity of ovariectomized rats. These data support our earlier findings that sexual dimorphism exists in baroreflex control of heart rate. More importantly, the present study provides experimental evidence that suggests a facilitatory role for estrogen in the modulation of baroreflex function.Key words: rat, gender, baroreflex sensitivity, 17 beta -estradiol, ovariectomy.

Gender difference in the Oatp1-mediated tubular reabsorption of estradiol 17β-d-glucuronide in rats

2002 ◽  
Vol 282 (6) ◽  
pp. E1245-E1254 ◽  
Author(s):  
Yasumasa Gotoh ◽  
Yukio Kato ◽  
Bruno Stieger ◽  
Peter J. Meier ◽  
Yuichi Sugiyama
Keyword(s):  
Gender Difference ◽  
Urinary Excretion ◽  
Glomerular Filtration ◽  
Hormonal Regulation ◽  
Organic Anion ◽  
Female Rats ◽  
Male Rats ◽  
Control Male ◽  
Male And Female Rats ◽  
Estradiol 17Β

The gender difference in the urinary excretion of estradiol-17β-glucuronide (E2-17βG) was examined in rats. The urinary clearance of E2-17βG was >250 times lower in male than in female rats. No such major gender difference was observed in its biliary excretion or metabolism in kidney homogenate. Both plasma protein binding and inulin clearance were comparable in male and female rats, suggesting that this gender difference cannot be explained by glomerular filtration. The urinary clearance with respect to the plasma unbound E2-17βG in male rats was <1% of the glomerular filtration rate, indicating its potential reabsorption by the kidney, and this increased to a level comparable with that found in female rats when dibromosulfophthalein was coinfused. A marked increase in E2-17βG urinary excretion was also observed in male rats that had undergone orchidectomy. Testosterone injections given to female rats reduced the urinary excretion to a level comparable with that of control male rats. The concomitant change in the expression of the gene product for organic anion-transporting polypeptide Oatp1, of which E2-17βG is a typical substrate, was found in the kidney membrane fractions after these treatments. These results suggest that urinary E2-17βG excretion is subject to hormonal regulation and that the large gender difference can be explained by regulation in Oatp1-mediated reabsorption.

Effects of thyroid hormone replacement on beta-adrenergic responsiveness of food-deprived rats

1986 ◽  
Vol 250 (5) ◽  
pp. R861-R867
Author(s):  
C. C. Barney ◽  
K. E. Wuertz ◽  
M. J. Katovich
Keyword(s):  
Heart Rate ◽  
Thyroid Hormone ◽  
Food Deprivation ◽  
Hormone Replacement ◽  
Male Rats ◽  
Beta Adrenergic ◽  
Glucose Levels ◽  
Cardiac Responses ◽  
Body Weights ◽  
Serum T4

Thyroid hormone levels and beta-adrenergic responsiveness after stimulation with the beta-adrenergic agonist isoproterenol were studied in four groups of male rats. The groups used were control rats, rats deprived of food for 72 h, rats administered 50 micrograms thyroxine (T4)/kg daily for 4 days, and rats deprived of food for 72 h and administered 50 micrograms T4/kg daily for 4 days. Food deprivation significantly decreased serum T4 and triiodothyronine (T3) levels, and administration of T4 significantly increased serum T4 and T3 levels in both fed and food-deprived rats. Administration of T4 led to lower body weights in both fed and food-deprived rats. Administration of isoproterenol led to increases in colonic and tail skin temperatures and heart rate. Food deprivation significantly attenuated the increased body temperatures and heart rate induced by isoproterenol, and administration of T4 to food-deprived rats returned these adrenergic responses to control levels. Administration of T4 to fed rats significantly increased the thermal and cardiac responses to isoproterenol above those of the control rats. Administration of isoproterenol also increased plasma glucose levels. Food deprivation significantly decreased both postsaline- and isoproterenol-stimulated glucose levels. However, administration of T4 was without effect on either the postsaline- or isoproterenol-stimulated glucose levels of either the fed or food-deprived rats. The decreases in T4 and T3 that accompany food deprivation may thus be responsible for some, but not all, of the reductions in beta-adrenergic responsiveness observed in food-deprived rats.

Acute effects of ethanol on baroreceptor reflex control of heart rate and on pressor and depressor responsiveness in rats

1987 ◽  
Vol 65 (5) ◽  
pp. 834-841 ◽  
Author(s):  
A-R. A. Abdel-Rahman ◽  
Roy Russ ◽  
J. A. Strickland ◽  
W. R. Wooles
Keyword(s):  
Heart Rate ◽  
Angiotensin Ii ◽  
Baroreflex Sensitivity ◽  
Pressor Response ◽  
Base Line ◽  
Response Curves ◽  
Baroreflex Control ◽  
Conscious Rats ◽  
Upward Shift ◽  
The Right

In rats anesthetized with α-chloralose, doses of 0.1, 0.5, and 1 g/kg of ethanol produced an upward shift of baroreflex curves constructed by plotting the heart rate response against mean arterial pressure following evoked rises in mean arterial pressures by phenylephrine or angiotensin II. Whereas the upward shift of baroreceptor curves may be related, at least in part, to a higher base-line heart rate after ethanol, the data showed that the 1 g/kg dose of ethanol significantly depressed baroreflex sensitivity, suggesting that higher doses of ethanol impair baroreflex-mediated bradycardia. The phenylephrine, but not the angiotensin II or the nitroprusside, dose–response curves were shifted to the right after ethanol, indicating a decreased pressor responsiveness and suggesting that ethanol may have α-adrenergic blocking activity. This effect was also obtained in conscious rats. That this effect was not influenced by changes in baroreflex sensitivity was supported by the finding that a similar shift of the phenylephrine pressor–response curve was obtained in bilaterally vagotomized and hexamethonium-treated rats. Whether this effect of ethanol on baroreflex control of heart rate was influenced by anesthesia was investigated in conscious rats; the 1 g/kg dose of ethanol that produced the most significant decrease in baroreflex sensitivity was used in these experiments. Ethanol was still able to significantly inhibit baroreflex sensitivity in conscious rats, but the upward shift of the baroreflex curve and the elevated base-line heart rate no longer occurred. On the other hand, none of the three doses of ethanol had any significant effect on baroreflex-mediated tachycardia (in response to nitroprusside-evoked hypotension). The data suggest that high doses of ethanol selectively inhibit baroreflex-mediated bradycardia and that ethanol has an α-blocking-like activity in conscious and anesthetized rats.

Apparent reduction in baroreflex sensitivity to adenosine in conscious dogs

1985 ◽  
Vol 249 (3) ◽  
pp. H554-H559 ◽  
Author(s):  
T. H. Hintze ◽  
F. L. Belloni ◽  
J. E. Harrison ◽  
G. C. Shapiro
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Muscarinic Receptor ◽  
Baroreflex Sensitivity ◽  
Systemic Arterial Pressure ◽  
Conscious Dogs ◽  
Beta Adrenergic ◽  
Apparent Reduction ◽  
Arterial Plasma ◽  
Plasma Adenosine

Relative effects of equihypotensive doses (-35 mmHg) of adenosine (5.0 mumol/kg) and nitroglycerin (25 micrograms/kg) on heart rate and, therefore, baroreflex sensitivity were studied in conscious dogs. Nitroglycerin increased heart rate 133 +/- 24% from 78 +/- 5.5 beats/min, whereas adenosine increased heart rate only 79 +/- 16% from 78 +/- 5.2 beats/min (P less than 0.01). Injection of nitroglycerin during combined beta-adrenergic and muscarinic receptor blockades caused arterial pressure to fall 38 +/- 3.4% from 107 +/- 3.2 mmHg without any significant change in heart rate (3.8 +/- 3.8 from 162 +/- 9.2 beats/min). During combined beta-adrenergic and muscarinic receptor blockades adenosine also reduced arterial pressure 45 +/- 2.7% from 106 +/- 2.9 mmHg but unexpectedly reduced heart rate as well by 37 +/- 1.7% from 160 +/- 9.7 beats/min. This bradycardia reflected an effect on the sinoatrial (SA) node rather than an induction of heart block, since the R-R interval increased by 70 +/- 7.8% from 371 +/- 20 ms (P less than 0.01), while the P-R interval increased only 13 +/- 2.3% from 97 +/- 7.2 ms (P less than 0.05) with no electrocardiographic evidence of nonconducted beats. Arterial plasma adenosine levels were 43 +/- 5 nmol/ml at this time. Adenosine also caused bradycardia during muscarinic blockade alone (-43 +/- 3.4% from 201 +/- 6.4 beats/min) and following bilateral vagal section (-33 +/- 1.9% from 151 +/- 5.9 beats/min). In summary, adenosine appears to alter normal baroreflex function in the conscious dog by reducing the tachycardia that normally follows a fall in systemic arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals 3486 Sex Differences in the Effects of Severe Food Restriction on Electrolyte Balance

2019 ◽  
Vol 3 (s1) ◽  
pp. 21-21
Author(s):  
Jonathas Fernandes Queiroz Almeida ◽  
Aline Souza ◽  
Hong Ji ◽  
Kathryn Sandberg
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sex Differences ◽  
Water Intake ◽  
Cardiac Injury ◽  
Female Rats ◽  
Male Rats ◽  
Free Access ◽  
Electrolyte Balance ◽  
Long Term Effects

OBJECTIVES/SPECIFIC AIMS: The goal of this study was to determine if there are any sex differences in the pathophysiological effects of sFR. METHODS/STUDY POPULATION: Male Fischer rats (4-month-old) were maintained on a control (CT) (ad libitum regular chow; n=8) or sFR (60% reduction of daily food intake, n=8) diet for 2 weeks. On days 1, 2, 3 and 14, the rats were placed in metabolic cages for food and water intake and 24-hour urine collection. Body weight (BW) is measured daily. After 2 weeks, the animals are given free access to normal chow for 3 months. Short-term and long-term effects of sFR on blood pressure and heart rate will be measured. RESULTS/ANTICIPATED RESULTS: After 2 weeks, the male CT group gained 7% BW (p <0.05), while BW in the sFR males was reduced by 12% (p<0.05 vs. CT). In contrast, female controls did not gain BW while the sFR females lost 18% of their BW. Water intake was reduced by 35%, which was similar to the reduction in females (p=0.18). The hematocrit of sFR male rats was higher (51.1%) than the CT group (45.2%, p<0.05), which was most likely due to the 6% reduction in plasma volume. A similar effect on hematocrit was observed in sRF females. Similarly, also to female rats, sFR had no effect on Na+ and K+ plasma or urine concentrations by day 14 in the male rats. DISCUSSION/SIGNIFICANCE OF IMPACT: sFR has similar effects on electrolyte balance in males and females. Ongoing studies will determine if there is any sex difference in the effects of sFR on blood pressure, heart rate and susceptibility to hypertension and cardiac injury.

Bupivacaine Inhibits Baroreflex Control of Heart Rate in Conscious Rats

2000 ◽  
Vol 92 (1) ◽  
pp. 197-197 ◽  
Author(s):  
Kyoung S. K. Chang ◽  
Don R. Morrow ◽  
Kazuyo Kuzume ◽  
Michael C. Andresen
Keyword(s):  
Heart Rate ◽  
Baroreflex Sensitivity ◽  
Cardiovascular Reflexes ◽  
Pulse Interval ◽  
Dependent Manner ◽  
Baroreflex Control ◽  
Conscious Rats ◽  
Reflex Bradycardia ◽  
Adrenergic Antagonist ◽  
Dose Dependent

Background Because exposure to intravenously administered bupivacaine may alter cardiovascular reflexes, the authors examined bupivacaine actions on baroreflex control of heart rate in conscious rats. Methods Baroreflex sensitivity (pulse interval vs. systolic blood pressure in ms/mmHg) was determined before, and 1.5 and 15.0 min after rapid intravenous administration of bupivacaine (0.5, 1.0, and 2.0 mg/kg) using heart rate changes evoked by intravenously administered phenylephrine or nitroprusside. The actions on the sympathetic and parasympathetic autonomic divisions of the baroreflex were tested in the presence of a muscarinic antagonist methyl atropine and a beta-adrenergic antagonist atenolol. Results Within seconds of injection of bupivacaine, mean arterial pressure increased and heart rate decreased in a dose-dependent manner. Baroreflex sensitivity was unaltered after administration of 0.5 mg/kg bupivacaine. In addition, 1 mg/kg bupivacaine at 1.5 min depressed phenylephrine-evoked reflex bradycardia (0.776 +/- 0.325 vs. 0.543 +/- 0.282 ms/mmHg, P &lt; 0.05) but had no effect on nitroprusside-induced tachycardia. Bupivacaine (2 mg/kg), however, depressed reflex bradycardia and tachycardia (phenylephrine, 0.751 +/- 0.318 vs. 0.451 +/- 0.265; nitroprusside, 0.839 +/- 0.256 vs. 0.564 +/- 0.19 ms/mmHg, P &lt; 0.05). Baroreflex sensitivity returned to prebupivacaine levels by 15 min. Bupivacaine (2 mg/kg), in the presence of atenolol, depressed baroreflex sensitivity (phenylephrine, 0.633 +/- 0.204 vs. 0.277 +/- 0.282; nitroprusside, 0.653 +/- 0.142 vs. 0.320 +/- 0.299 ms/mmHg, P &lt; 0.05). In contrast, bupivacaine did not alter baroreflex sensitivity in the presence of methyl atropine. Conclusions Bupivacaine, in clinically relevant concentrations, inhibits baroreflex control of heart rate in conscious rats. This inhibition appears to involve primarily vagal components of the baroreflex-heart rate pathways.

BLOOD AMINO ACID STUDIES: II. EFFECTS OF DIETARY LYSINE CONCENTRATION, SEX, AND GROWTH RATE ON PLASMA FREE LYSINE AND THREONINE LEVELS IN THE RAT

1961 ◽  
Vol 39 (11) ◽  
pp. 1675-1680 ◽  
Author(s):  
A. B. Morrison ◽  
E. J. Middleton ◽  
J. M. McLaughlan
Keyword(s):  
Growth Rate ◽  
Corn Oil ◽  
Maximum Growth ◽  
Reciprocal Relationship ◽  
Female Rats ◽  
Male Rats ◽  
Maximum Plasma ◽  
Lower Plasma ◽  
Deficient Diet ◽  
Lysine Concentration

Plasma free lysine levels of growing female rats given a lysine-deficient diet supplemented with graded amounts of lysine were higher than those of males. In both sexes, plasma free lysine values rose rapidly in response to added dietary lysine, and reached a maximum at a dietary lysine concentration of approximately 1.0%. This amount of dietary lysine was about 0.2% greater than that found necessary for maximum growth. Male rats given diets containing rapeseed oil and graded amounts of lysine showed reduced growth and lower plasma lysine and threonine levels as compared to animals given similar diets containing corn oil, but the amount of dietary lysine required for maximum plasma lysine levels was not influenced by the growth rate. Plasma free threonine levels showed a reciprocal relationship with those for lysine. It was concluded that measurement of the ratio between plasma free lysine and threonine levels may provide a sensitive indication of the adequacy of the dietary lysine content.

scholarly journals Gender and gonadal influences on ghrelin mRNA levels in rat stomach

2001 ◽  
pp. 687-690 ◽  
Author(s):  
O Gualillo ◽  
JE Caminos ◽  
M Kojima ◽  
K Kangawa ◽  
E Arvat ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Gonadal Hormones ◽  
Female Rats ◽  
Male Rats ◽  
Mrna Levels ◽  
Rat Stomach ◽  
Adult Rats ◽  
Stable Level ◽  
Young Rats

OBJECTIVE: The recently isolated endogenous GH secretagogue, named ghrelin, is a gastric peptide of 28 amino acids with an n-octanoylation in the serine 3 that confers the biological activity to this factor. Ghrelin has been shown to directly stimulate GH release in vivo and in vitro and to be involved in the regulation of gastric acid secretion and motility. In the present work we have studied gender and gonadal dependency of ghrelin mRNA expression in rat stomach. DESIGN AND METHODS: We analysed ghrelin mRNA expression in rat stomach by Northern blot analysis. We also examined the effect of gonadal steroid deprivation on ghrelin mRNA expression. RESULTS AND CONCLUSIONS: The results obtained showed clearly that ghrelin gastric mRNA expression increased with age in young rats (up to 90 days old) but exhibited no significant sex difference at each age tested. Ghrelin mRNA levels were lowest at postnatal day 9, reaching a stable level of expression at day 40 in both female and male rats, although the increase in female rats appears much more gradual than that in males. Moreover, neither ovariectomy nor orchidectomy significantly modified ghrelin mRNA gastric levels in adult rats. In conclusion, these data indicate that ghrelin mRNA expression is associated with age and that a progressive increase is present from the perinatal period up to a stable level after puberty. Gonadal hormones did not alter ghrelin mRNA levels. Taken together, these data showed that ghrelin mRNA levels in young rats are age but not gender dependent, and are not influenced by gonadal steroids.

Gender differences in the cardiac response to dietary conjugated linoleic acid isomers

2006 ◽  
Vol 84 (2) ◽  
pp. 257-264 ◽  
Author(s):  
Paramjit S. Tappia ◽  
Rabban Mangat ◽  
Cindy Gabriel ◽  
Melissa R. Dent ◽  
Nina Aroutiounova ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Heart Rate ◽  
Heart Function ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Female Rats ◽  
Male Rats ◽  
Control Group ◽  
Ventricular Systolic Pressure ◽  
Left Ventricular Systolic Pressure

The present study was undertaken to assess the heart function, by the in vivo catheterization technique, of healthy male and female Sprague–Dawley rats fed different conjugated linoleic acid (CLA) isomers, (cis-9, trans-11 (c9,t11) and trans-10, cis-12 (t10,c12)) individually and in combination (50:50 mix as triglyceride or fatty acids) from 4 to 20 weeks of age. Whereas the triglyceride form of the CLA isomer mix lowered the heart rate, the rate of contraction (+dP/dt) and rate of relaxation (–dP/dt), systolic and diastolic pressures, mean arterial pressure, and the left ventricular systolic pressure were higher in male rats as compared with all the other dietary groups. In contrast, there were no significant effects in the cardiac function of the female rats in response to the CLA isomer mix in triglyceride form. Whereas the heart rate, +dP/dt, and left ventricular systolic pressure were lower in male rats fed the t10,c12 CLA isomer alone, the heart rate of the female rats was higher, but the systolic pressure, +dP/dt, and mean arterial pressure were lower compared with the control group. Also, the left ventricular end-diastolic pressure was specifically higher in the female rats in response to free fatty acids-containing CLA mix. Furthermore, an additive effect of the free fatty acids-containing CLA mix was seen in the +dP/dt and –dP/dt of female rats compared with the control group. These results indicate that CLA isomers exert differential effects on heart function and suggest the need for a complete evaluation of the benefits, interactions, and potential side effects of each isomer.

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