Influence of the estrous cycle on the sensitivity to catecholamines in right atria from rats submitted to foot-shock stress

1996 ◽  
Vol 74 (6) ◽  
pp. 670-678 ◽  
Author(s):  
L.C.M. Vanderlei ◽  
F.K. Marcondes ◽  
L.L.B. Lanza ◽  
R.C. Spadari-Bratfisch
Keyword(s):  
Estrous Cycle ◽  
Right Atria ◽  
Shock Stress

Pharmacological evidence for β2-adrenoceptor in right atria from stressed female rats

1999 ◽  
Vol 77 (6) ◽  
pp. 432-440 ◽  
Author(s):  
R C Spadari-Bratfisch ◽  
I N Santos ◽  
LCM Vanderlei ◽  
F K Marcondes
Keyword(s):  
Estrous Cycle ◽  
Model Equation ◽  
Female Rats ◽  
Cycle Phase ◽  
Response Curves ◽  
Chronotropic Response ◽  
Site Model ◽  
Stressed Female ◽  
Right Atria ◽  
Shock Stress

The purpose of the present study was to demonstrate a physiological response to TA2005, a potent β2-adrenoceptor (β2-AR) selective agonist, in right atria isolated from stressed female rats under the influence of the estrous cycle. We obtained concentration-response curves to the agonist in the presence and in the absence of selective antagonists in right atria isolated from female rats submitted to three daily foot-shock sessions (30 min duration, 120 pulses of 1.0 mA, 1.0 s, applied at random intervals of 5-25 s) and sacrificed at estrus or diestrus. Our results showed that the pD2 values of TA2005 were not influenced by estrous cycle phase or foot-shock stress. However, in right atria from stressed rats sacrificed during diestrus, the concentration-response curve to TA2005 was biphasic, with a response being obtained at concentrations of 0.1 nM, whereas during estrus no response was observed at doses lower than 3 nM. ICI118,551, a β2-AR antagonist, abolished the response to nanomolar concentrations of TA2005 in right atria from stressed rats at diestrus, with no changes in agonist pD2 values in right atria from control rats (7.47 ± 0.09, p > 0.05) but a 3-fold decrease in pD2 values of TA2005 in right atria from foot shock stressed rats (7.90 ± 0.07, p [Formula: see text] 0.05). Concentration-response curves to TA2005 in the presence of ICI118,551 were best fitted by a one-site model equation. The β1-AR antagonist, CGP20712A, shifted to the right only the second part of the concentration-response curves to the agonist, unmasking the putative β2-AR-mediated response to the agonist in tissues isolated from stressed rats at diestrus. Under this condition, concentration-response curves to the agonist were best fitted by a two-site model equation. pD2 and maximum response of TA2005 interaction with β1- and putative β2-adrenoceptor components were calculated. Schild analyses gave a pKB value for CGP20712A that was typical for the interaction with β1-AR in each experimental group. pKB values for ICI118,551 could not be obtained in stressed rats sacrificed at diestrus since Schild plot slopes were lower than 1.0. In right atria from control rats, ICI118,551 pKB values were similar to reported values for the interaction of the antagonist with β1-AR. These results confirm that a heterogenous β-AR population mediating the chronotropic response to catecholamines can be demonstrated in right atria from foot shock stressed female rats sacrificed at diestrus. The stress-induced response seems to be mediated by the β2-AR subtype. Right atria from rats sacrificed during estrus are protected against stress-induced alterations on the homogeneity of β-AR population.Key words: foot-shock stress, TA2005, ICI118,551, CGP20712A, estrus, diestrus.

Relationship among sensitivity to adrenaline, plasma corticosterone level; and estrous cycle in rats

1995 ◽  
Vol 73 (5) ◽  
pp. 602-607 ◽  
Author(s):  
M. L. V. Rodrigues ◽  
F. K. Marcondes ◽  
R. C. Spadari-Bratfisch
Keyword(s):  
Estrous Cycle ◽  
Dose Response ◽  
Corticosterone Level ◽  
Plasma Corticosterone ◽  
Female Rats ◽  
Extraneuronal Uptake ◽  
Response Curves ◽  
Experimental Conditions ◽  
Dose Response Curves ◽  
Right Atria

The dose–response curves to the chronotropic effect of adrenaline obtained in right atria isolated from female rats indicated an order of increasing sensitivity to adrenaline, at the pD2 level, according to the estrous cycle, as follows: estrus ≤ metestrus ≤ diestrus ≤ proestrus. Inhibition of neuronal and extraneuronal uptake shifted the dose–response curves to adrenaline to the left only in right atria isolated from rats during estrus or metestrus. Moreover, under these experimental conditions, right atria were subsensitive to adrenaline during proestrus, in contrast to metestrus. Plasma corticosterone levels were lower during estrus and higher at proestrus. There was a positive correlation between right atria sensitivity to adrenaline and plasma corticosterone levels and estrous cycle phases. Our results also suggest that in the rat right atria during proestrus, as opposed to the other phases of the estrous cycle, there was an endogenous inhibition of extraneuronal uptake together with some alteration at the adrenoceptor level and (or) at intracellular mechanisms beyond receptors.Key words: adrenergic response, female, adrenaline, chronotropism, right atria.

Functional β2-adrenoceptors in rat left atria: effect of foot-shock stress

2017 ◽  
Vol 95 (9) ◽  
pp. 999-1008 ◽  
Author(s):  
André Luiz de Moura ◽  
Stephen Hyslop ◽  
Dora M. Grassi-Kassisse ◽  
Regina C. Spadari
Keyword(s):  
Receptor Antagonist ◽  
Adenylyl Cyclase ◽  
Left Atrial ◽  
Male Rats ◽  
Inotropic Response ◽  
Chronotropic Effect ◽  
Adenylyl Cyclase Activity ◽  
Altered Sensitivity ◽  
Right Atria ◽  
Shock Stress

Altered sensitivity to the chronotropic effect of catecholamines and a reduction in the β1/β2-adrenoceptor ratio have previously been reported in right atria of stressed rats, human failing heart, and aging. In this report, we investigated whether left atrial inotropism was affected by foot-shock stress. Male rats were submitted to 3 foot-shock sessions and the left atrial inotropic response, adenylyl cyclase activity, and β-adrenoceptor expression were investigated. Left atria of stressed rats were supersensitive to isoprenaline when compared with control rats and this effect was abolished by ICI118,551, a selective β2-receptor antagonist. Schild plot slopes for the antagonism between CGP20712A (a selective β1-receptor antagonist) and isoprenaline differed from unity in atria of stressed but not control rats. Atrial sensitivity to norepinephrine, as well as basal and forskolin- or isoprenaline-stimulated adenylyl cyclase activities were not altered by stress. The effect of isoprenaline on adenylyl cyclase stimulation was partially blocked by ICI118,551 in atrial membranes of stressed rats. These findings indicate that foot-shock stress equally affects inotropism and chronotropism and that β2-adrenoceptor upregulation contributes to the enhanced inotropic response to isoprenaline.

Chronotropic response to (±)-CGP12177 in right atria of stressed rats

2001 ◽  
Vol 79 (5) ◽  
pp. 393-399 ◽  
Author(s):  
I N Santos ◽  
R C Spadari-Bratfisch
Keyword(s):  
Response Curve ◽  
Response Curves ◽  
Stimulant Effect ◽  
Chronotropic Response ◽  
Stress Changes ◽  
Random Intervals ◽  
The Right ◽  
Right Atria ◽  
Concentration Response Curve ◽  
Shock Stress

Foot-shock stress changes the sensitivity of the rat right atria to β1- and β2-adrenoceptor (AR) agonists. We investigated whether the same stress protocol also changes the atrial sensitivity to the non conventional agonist, (±)-CGP12177. Concentration-response curves to (±)-CGP12177, a β1- and β2-adrenoceptor antagonist with agonist properties at the putative β4-adrenoceptors, were obtained in the absence and presence of propranolol (200 nM or 2 µM), CGP20712A 10 nM plus ICI118,551 50 nM, or CGP20712A (1 µM or 3 µM), in right atria from rats submitted to three daily foot-shock sessions (120 mA pulses of 1.0 s duration applied at random intervals of 5-25 s over 30 min) and killed after the third session. The pD2 for (±)-CGP12177 was not influenced by foot-shock stress. The stimulant effect of (±)-CGP12177 was resistant to blockade by 200 nM and 2 µM (±)-propranolol, and to combined blockade by CGP20712A and ICI118,551. However, in right atria from stressed rats given 200 nM propranolol, the concentration-response curve to the agonist was shifted 2.0-fold to the right. CGP20712A shifted the concentration-response curve to (±)-CGP12177 to the right by 4.6- (1 µM) and 19-fold (3 µM) in atria of control rats, and by 2.2- (1 µM) and 43-fold (3 µM) in atria of stressed rats. Maximum response to CGP12177 was not affected by propranolol or CGP20712A in concentrations ranging from 0.1 nM to 10 µM. These results show that the chronotropic effect of (±)-CGP12177 is mediated by atypical β4-adrenoceptors. In constrast with to β1-and (or) β2-AR, this receptor is resistant to the effects of foot-shock stress, suggesting that the putative β4-AR is a different receptor from a low affinity state of β1-adrenoceptor, as previously proposed, unless both proposed isoforms of β1-adrenoceptor show independent stress-induced behavior.Key words: putative β4-adrenoceptor, low affinity β1-adrenoceptor isoform, stress, right atria, chronotropic response.

The β-adrenoceptor site activated by CGP12177 varies in behavior according to the estrous cycle phase and stress

2003 ◽  
Vol 81 (5) ◽  
pp. 459-468 ◽  
Author(s):  
I N Santos ◽  
F K Marcondes ◽  
R C Spadari-Bratfisch
Keyword(s):  
Estrous Cycle ◽  
Stress Hormones ◽  
Serum Levels ◽  
Female Rats ◽  
Cycle Phase ◽  
Response Curves ◽  
Chronotropic Response ◽  
The Right ◽  
Right Atria ◽  
Group Serum

The aim of this work was to assess whether stress and estrous cycle phases affected the β-adrenoceptor (β-AR) site activated by CGP12177 in the right atria of rats. The chronotropic response to CGP12177 in the absence or presence of antagonists was determined in atria from rats submitted to one daily foot-shock session for 3 consecutive days. Blood was collected for hormonal assays. The pD2 for CGP12177 in atria from females was lower than in atria from males and was unaltered by stress or the estrous cycle. Propranolol (200 nM) or CGP20712A (3 μM) shifted the concentration–response curves to CGP12177 to the right in control and stressed estrus or control diestrus rats. Atria from stressed diestrus rats were resistant to blockade by propranolol or CGP20712A, indicating that the effect of β-adrenoceptor antagonists on the response to CGP12177 is influenced by estrous cycle phases. The stress-induced increase in serum corticosterone levels was independent of the estrous cycle or gender, but the estradiol/progesterone ratio was affected differently in the two groups of female rats. In the diestrus group, serum estradiol levels decreased after the first foot-shock session and remained low until the day of sacrifice, whereas in the estrus group the serum levels of estradiol did not decrease after stress and peaked on the second day, which corresponded to proestrus. These data do not indicate whether there is a direct or indirect effect of stress hormones and (or) sex steroids on cardiac β-AR sensitivity. However, they do show that the classic and low-affinity binding sites of the β-AR are independently regulated and that the β-AR atypical site affinity for antagonists depends on the estrous cycle.Key words: allosterism, β-adrenoceptor, β-adrenoceptor, receptor active site, steroid hormones, stress.

Detection of atrial natriuretic peptides (ANP) in rat atria by immunogold-silver staining (IGSS)

1994 ◽  
Vol 52 ◽  
pp. 304-305
Author(s):  
Robyn Rufner ◽  
Gerhard W. Hacker ◽  
Michele Forte ◽  
Nancyleigh E. Carson ◽  
Cristina Xenachis ◽  
...  
Keyword(s):  
Natriuretic Peptides ◽  
Silver Staining ◽  
Sodium Thiosulfate ◽  
Atrial Natriuretic Peptides ◽  
Paraffin Sections ◽  
Glass Slides ◽  
Metallic Salts ◽  
Wistar Kyoto ◽  
Right Atria

The use of immunogold-silver staining (IGSS) to enhance label penetration and Localization for immunocytochemistry or in situ hybridization utilizing a variety of metallic salts has been documented. In this morphological study, the effects of silver acetate, silver lactate and silver nitrate were evaluated for immunogold-labeling of a trial natriuretic peptides (ANP) in rat right atria.Eight Wistar Kyoto retired breeders were sedated with pentobarbital, perfused with either 4% paraformaldehyde (LM) or Karnovsky's fixative (EM), and right atria were dissected, processed, embedded in paraffin or epon, respectively and sectioned according to conventional methods. For light microscopy, an indirect IGSS method according to Hacker (3) was performed. Paraffin sections on glass slides were washed in ddH2O, immersed in Lugol's iodine, washed in ddH2O and treated with 2.5% aqueous sodium thiosulfate for 20 sec. After additional washes in ddH2O and TBS-0.1% fish gelatin, 10% normal goat serum (PBS with 1% BSA) was applied for 20 min before an overnight incubation at 4°C with a polyclonal α-ANP primary antibody (Peninsula Labs, 1:1000 in TBS/BSA).

Rat Ovarian Renin: Characterization and Changes during the Estrous Cycle*

Endocrinology ◽  
1988 ◽  
Vol 123 (5) ◽  
pp. 2331-2340 ◽  
Author(s):  
RANDY B. HOWARD ◽  
ANTHONY G. PUCELL ◽  
F. MERLIN BUMPUS ◽  
AHSAN HUSAIN
Keyword(s):  
Estrous Cycle
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