scholarly journals Alpha-adrenergic stimulation of potassium efflux in guinea-pig hepatocytes may involve calcium influx and calcium release.

1984 ◽  
Vol 346 (1) ◽  
pp. 395-407 ◽  
Author(s):  
L M DeWitt ◽  
J W Putney
Keyword(s):  
Guinea Pig ◽  
Calcium Release ◽  
Calcium Influx ◽  
Adrenergic Stimulation ◽  
Potassium Efflux ◽  
Stimulation Of

scholarly journals Phosphorylation of phospholipids in isolated guinea pig hearts stimulated with isoprenaline

1988 ◽  
Vol 251 (1) ◽  
pp. 189-194 ◽  
Author(s):  
G Jakab ◽  
S T Rapundalo ◽  
R J Solaro ◽  
E G Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Total Phospholipid ◽  
Fold Increase ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Adrenergic Agents ◽  
32P Incorporation ◽  
Phosphate Incorporation ◽  
Stimulation Of

Phosphorylation of phospholipids was studied in Langendorff perfused guinea pig hearts subjected to beta-adrenergic stimulation. Hearts were perfused with Krebs-Henseleit buffer containing [32P]Pi and freeze-clamped in a control condition or at the peak of the inotropic response to isoprenaline. 32P incorporation into total phospholipids, individual phospholipids and polyphosphoinositides was analysed in whole tissue homogenates and membranes, enriched in sarcoplasmic reticulum, prepared from the same hearts. Isoprenaline stimulation of the hearts did not result in any significant changes in the levels of phosphate incorporation in the total phospholipid present in cardiac homogenates (11.6 +/- 0.4 nmol of 32P/g for control hearts and 12.4 +/- 0.5 nmol of 32P/g for isoprenaline-treated hearts; n = 6), although there was a significant increase in the degree of phospholipid phosphorylation in sarcoplasmic reticulum (3.5 +/- 0.3 nmol of 32P/mg for control hearts and 6.7 +/- 0.2 nmol of 32P/mg for isoprenaline-treated hearts; n = 6). Analysis of 32P incorporation into individual phospholipids and polyphosphoinositides revealed that isoprenaline stimulation of the hearts was associated with a 2-3-fold increase in the degree of phosphorylation of phosphatidylinositol monophosphate and bisphosphate as well as phosphatidic acid in both cardiac homogenates and sarcoplasmic reticulum membranes. In addition, there was increased phosphate incorporation into phosphatidylinositol in sarcoplasmic reticulum membranes. Thus, perfusion of guinea pig hearts with isoprenaline is associated with increased formation of polyphosphoinositides and these phospholipids may be involved, at least in part, in mediating the effects of beta-adrenergic agents in the mammalian heart.

The effect of isoproterenol on isolated muskrat and guinea pig hearts

1986 ◽  
Vol 64 (12) ◽  
pp. 2674-2677 ◽  
Author(s):  
Thomas A. McKean
Keyword(s):  
Heart Rate ◽  
Guinea Pig ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Ventricular Pressure ◽  
Adrenergic Stimulation ◽  
Potential Predator ◽  
Opposing Effects ◽  
Sympathetic Effect ◽  
Stimulation Of

Isoproterenol, a β-adrenergic agonist, was given by bolus injection to Langendorff-perfused muskrat and guinea pig hearts. Bolus content ranged from 18 to 29 200 pmol. The hearts responded by increasing left ventricular pressure, heart rate, and release of lactate. The drug threshold was similar for the hearts of the two species but the magnitude of the response differed both at threshold and at saturation doses. The increase in left ventricular pressure and heart rate was greater in guinea pig hearts compared with muskrat hearts. Lactate release was stimulated earlier and increased more in muskrat hearts compared with guinea pig hearts. The weak β-adrenergic stimulation of heart rate and left ventricular pressure in the muskrat may be of benefit when the animal dives to escape a potential predator. Under these conditions of fear, exercise, hypoxia, and diving there would be opposing effects of sympathetic versus vagal stimulation of the myocardium. The sympathetic effect would be to increase myocardial oxygen consumption while the vagal effect would be to reduce it. In the diving mammal the vagal effect predominates and this may be augmented by a blunted rate and pressure response to β-stimulation.

Intracellular mechanisms mediating reversal of beta-adrenergic stimulation in intact beating hearts

1993 ◽  
Vol 264 (3) ◽  
pp. H791-H797 ◽  
Author(s):  
L. Talosi ◽  
I. Edes ◽  
E. G. Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Troponin I ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Dependent Protein ◽  
Camp Levels ◽  
Isoproterenol Infusion ◽  
Phosphate Incorporation ◽  
Stimulation Of

The changes in 32P labeling of phosphoproteins were studied in Langendorff-perfused guinea pig hearts during reversal of the stimulatory effects of isoproterenol. Exposure of the hearts to isoproterenol was associated with significant increases in adenosine 3',5'-cyclic monophosphate (cAMP) levels and in the phosphate incorporation into phospholamban in sarcoplasmic reticulum, the 15-kDa protein in the sarcolemma, and troponin I in the myofibrils. Phospholamban was phosphorylated on serine and threonine residues, both of which are sites for cAMP-dependent and Ca(2+)-calmodulin-dependent protein kinases, respectively. Termination of isoproterenol infusion was associated with reversal of the mechanical effects of isoproterenol stimulation and reversal of the increases in tissue cAMP levels. However, the decreases in cAMP levels correlated only with dephosphorylation of phosphoserine in phospholamban. Dephosphorylation of phosphothreonine in phospholamban, the 15-kDa sarcolemmal protein, and troponin I occurred at a slower rate. These findings suggest that cAMP-dependent phosphorylation of phospholamban (phosphoserine) may play a prominent role during beta-adrenergic stimulation of intact hearts.

scholarly journals Proteolytic cleavage and PKA phosphorylation of α1C subunit are not required for adrenergic regulation of CaV1.2 in the heart

2017 ◽  
Vol 114 (34) ◽  
pp. 9194-9199 ◽  
Author(s):  
Alexander Katchman ◽  
Lin Yang ◽  
Sergey I. Zakharov ◽  
Jared Kushner ◽  
Jeffrey Abrams ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Molecular Mechanisms ◽  
Calcium Influx ◽  
Phosphorylation Site ◽  
Proteolytic Cleavage ◽  
Phosphorylation Sites ◽  
Adrenergic Stimulation ◽  
Adrenergic Regulation ◽  
Voltage Dependent ◽  
Stimulation Of

Calcium influx through the voltage-dependent L-type calcium channel (CaV1.2) rapidly increases in the heart during “fight or flight” through activation of the β-adrenergic and protein kinase A (PKA) signaling pathway. The precise molecular mechanisms of β-adrenergic activation of cardiac CaV1.2, however, are incompletely known, but are presumed to require phosphorylation of residues in α1C and C-terminal proteolytic cleavage of the α1C subunit. We generated transgenic mice expressing an α1C with alanine substitutions of all conserved serine or threonine, which is predicted to be a potential PKA phosphorylation site by at least one prediction tool, while sparing the residues previously shown to be phosphorylated but shown individually not to be required for β-adrenergic regulation of CaV1.2 current (17-mutant). A second line included these 17 putative sites plus the five previously identified phosphoregulatory sites (22-mutant), thus allowing us to query whether regulation requires their contribution in combination. We determined that acute β-adrenergic regulation does not require any combination of potential PKA phosphorylation sites conserved in human, guinea pig, rabbit, rat, and mouse α1C subunits. We separately generated transgenic mice with inducible expression of proteolytic-resistant α1C. Prevention of C-terminal cleavage did not alter β-adrenergic stimulation of CaV1.2 in the heart. These studies definitively rule out a role for all conserved consensus PKA phosphorylation sites in α1C in β-adrenergic stimulation of CaV1.2, and show that phosphoregulatory sites on α1C are not redundant and do not each fractionally contribute to the net stimulatory effect of β-adrenergic stimulation. Further, proteolytic cleavage of α1C is not required for β-adrenergic stimulation of CaV1.2.

Sign in / Sign up

Export Citation Format

Share Document