Potentiation of toxicity and positive inotropic effect of ouabain by furosemide in guinea pig heart.

1982 ◽  
Vol 7 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Masaru MINAMI ◽  
Masayuki SAKURAI ◽  
Katsushi KANAMORI ◽  
Atsushi MIYAMOTO ◽  
Takeshi KOBAYASHI ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Positive Inotropic Effect ◽  
Inotropic Effect ◽  
Guinea Pig Heart ◽  
Potentiation Of Toxicity

Roles of PKA, PI3K, and cPLA2 in the NO-mediated negative inotropic effect of β2-adrenoceptor agonists in guinea pig right papillary muscles

2008 ◽  
Vol 294 (1) ◽  
pp. C106-C117 ◽  
Author(s):  
Fabien A. Faucher ◽  
François E. Gannier ◽  
Jacques M. Lignon ◽  
Pierre Cosnay ◽  
Claire O. Malécot
Keyword(s):  
Guinea Pig ◽  
Positive Inotropic Effect ◽  
Negative Inotropic Effect ◽  
Inotropic Effect ◽  
Papillary Muscles ◽  
Guinea Pig Heart ◽  
Inotropic Effects ◽  
Inotropic State ◽  
No Release ◽  
High Concentrations

Although β2-adrenoceptors represent 15–25% of β-adrenoceptors in the guinea pig heart, their functionality is controversial. We assessed the inotropic effects of β2-adrenoceptor partial agonists in right papillary muscles. Salbutamol induced a small but significant concentration-dependent negative inotropic effect (NIE, −5% at 60 nM) followed by a moderate positive inotropic effect (+36% at 6 μM) due to activation of β1-adrenoceptors. In the presence of 4 μM atenolol, the concentration-dependent NIE (−12% at 6 μM) was biphasic, best described by a double logistic equation with respective EC50 values of 3 and ∼420 nM, and was insensitive to SR59230A. In muscles from pertussis toxin-treated guinea pigs, the salbutamol-induced positive inotropic effect was sensitive to low concentrations of ICI-118551 in an unusual manner. Experiments in reserpinized animals revealed the importance of the phosphorylation-dephosphorylation processes. PKA inhibition reduced and suppressed the effects obtained at low and high concentrations, respectively, indicating that its activation was a prerequisite to the NIE. The effect occurring at nanomolar concentrations depended upon PKA/phosphatidylinositol 3-kinase/cytosolic phospholipase A2 (cPLA2) activations leading to nitric oxide (NO) release via the arachidonic acid/cyclooxygenase pathway. NO release via PKA-dependent phosphorylation of the receptor was responsible for the inotropic effect observed at submicromolar concentrations, which is negatively controlled by cPLA2. The possibility that these effects are due to an equilibrium between different affinity states of the receptor (Gs/Gi coupled and Gi independent with different signaling pathways) that can be displaced by ICI-118551 is discussed. We conclude that β2-adrenoceptors are functional in guinea pig heart and can modulate the inotropic state.

Positive inotropic effect of carcinine in the isolated perfused guinea pig heart

1990 ◽  
Vol 18 (3) ◽  
pp. 317-321 ◽  
Author(s):  
DAVID N. BROTMAN ◽  
LOUIS FLANCBAUM ◽  
YOUNG-HEE KANG ◽  
GARY F. MERRILL ◽  
HANS FISHER
Keyword(s):  
Guinea Pig ◽  
Positive Inotropic Effect ◽  
Inotropic Effect ◽  
Guinea Pig Heart

Influence of lithium on the positive inotropic effect of phenylephrine and isoprenaline in guinea-pig heart

1988 ◽  
Vol 150 (1-2) ◽  
pp. 123-129 ◽  
Author(s):  
Laura Mantelli ◽  
Lucia Capanni ◽  
Vittorio Corti ◽  
Federico Bennardini ◽  
Rosanna Matucci ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Positive Inotropic Effect ◽  
Inotropic Effect ◽  
Guinea Pig Heart

Studies on the positive inotropic effect of dopamine in the guinea-pig heart

1977 ◽  
Vol 301 (1) ◽  
pp. 49-55 ◽  
Author(s):  
A. Mugelli ◽  
F. Ledda ◽  
Laura Mantelli ◽  
M. Torrini ◽  
Tiziana Maccioni
Keyword(s):  
Guinea Pig ◽  
Positive Inotropic Effect ◽  
Inotropic Effect ◽  
Guinea Pig Heart

Functional and autoradiographic characterization of dopamine D2-like receptors in the guinea pig heart

2002 ◽  
Vol 80 (6) ◽  
pp. 578-587 ◽  
Author(s):  
María de Jesús Gómez ◽  
Guy Rousseau ◽  
Réginald Nadeau ◽  
Roberto Berra ◽  
Gonzalo Flores ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Western Blot ◽  
Dopamine Receptors ◽  
Negative Inotropic Effect ◽  
Cyclase Activity ◽  
Inotropic Effect ◽  
Receptor Subtypes ◽  
Guinea Pig Heart ◽  
Additional Information ◽  
The Right

Dopamine receptors include the D1- (D1 and D5 subtypes) and D2-like (D2, D3, and D4 subtypes) families. D1-like receptors are positively and D2-like receptors negatively coupled to the adenylyl cyclase. Dopamine D2-like (D4 subtype) receptors have been identified in human and rat hearts. However the presence of D2 and D3 receptor subtypes is unclear. Furthermore, their role in cardiac functions is unknown. By autoradiographic studies of guinea pig hearts, we identified D3 and D4 receptors, using the selective radioligands [3H]-7-OH-DPAT and [3H]emonapride (YM-09151-2 plus raclopride). Western blot analysis confirmed D3 and D4 receptors in the right and left ventricle of the same species. Selective agonists of D3 and D4 receptors (±)-7-OH-DPAT and PD 168 077 (10–9 to 10–5 M, respectively) induced a significant negative chronotropic and inotropic effect in the isolated guinea pig heart preparation. Negative inotropic effect induced by PD 168 077 was associated with an inhibition in cyclase activity. No changes in cyclase activity were found with (±)-7-OH-DPAT. The aim of this study is to support the presence of D3 and D4 receptors in the heart. Although our results suggest that D3 and D4 receptors are functionally active in the heart, we need additional information with an antagonist and an agonist of improved potency and selectivity to understand the respective roles of D3 and D4 receptors in the cardiac functions.Key words: Dopamine receptors (D2, D3, D4 subtypes), autoradiography, Western blot, cAMP, heart.

Calcium channels and excitation–contraction coupling in cardiac cells. II. A pharmacological study of the biphasic contraction in guinea-pig papillary muscle

1987 ◽  
Vol 65 (9) ◽  
pp. 1832-1839 ◽  
Author(s):  
E. Honoré ◽  
M. M. Adamantidis ◽  
B. A. Dupuis ◽  
C. E. Challice ◽  
P. Guilbault
Keyword(s):  
Guinea Pig ◽  
Papillary Muscle ◽  
Positive Inotropic Effect ◽  
Pharmacological Study ◽  
Negative Inotropic Effect ◽  
Cardiac Cells ◽  
Inotropic Effect ◽  
Free Solution ◽  
Contraction Coupling ◽  
Rich Solution

Biphasic contractions were obtained in guinea-pig papillary muscle by inducing partial depolarization in K+-rich solution (17 mM) in the presence of 0.3 μM isoproterenol. Mn2+ ions inhibited the two components of contraction in a similar way. Nifedipine and particularly Cd2+ ions specifically inhibited the second component of contraction. Isoproterenol and BAY K 8644 markedly increased the amplitude of the second component (P2) of contraction. Nevertheless, a moderate positive inotropic effect of isoproterenol was found on the first component (P1) of contraction when excitability was restored by 0.2 mM Ba instead of isoproterenol. Acetylcholine and hypoxia decreased the amplitude of the second component of contraction to a greater extent. In the presence of digoxin or Na+-free solution, P1was strongly increased. When sarcoplasmic reticular function was hindered by 1 mM caffeine or in the presence of Ca2+-free Sr2+ solution, digoxin always induced a negative inotropic effect on P2. Inversely in these conditions the transient positive inotropic effect of Na+-free solution was strongly reduced. These results are consistent with the hypothesis that the late component of contraction is triggered by the slow inward Ca2+ current and that the early component is due to Ca2+ release from the sarcoplasmic reticulum.

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