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Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
Published on: September 17, 2015
Prolactin-releasing peptide regulates cardiac contractility
Attila Kónyi1, Réka Skoumal, Anna-Maria Kubin
1Heart Institute, Medical School, University of Pécs, Pécs, Hungary.
Regulatory Peptides
|July 21, 2009
Summary
Prolactin-releasing peptide (PrRP) directly enhances heart muscle contraction. This novel cardiovascular role of PrRP is independent of cAMP and involves complex interactions with protein kinase C alpha and protein phosphatase 1.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Molecular Cardiology
Background:
- Specific prolactin-releasing peptide (PrRP) binding sites are abundant in the heart muscle (myocardium).
- The precise function of PrRP in regulating cardiac activity remains largely uncharacterized.
Purpose of the Study:
- To investigate the functional role of PrRP in the regulation of cardiac function.
- To elucidate the signaling pathways mediating the cardiac effects of PrRP.
Main Methods:
- Utilized isolated perfused rat hearts to assess cardiac contractility.
- Administered varying concentrations of PrRP and specific enzyme inhibitors (IBMX, calyculin A, okadaic acid, Ro32-0432).
- Measured changes in myocardial contractility and phospholamban phosphorylation.
Main Results:
- Infusion of PrRP produced a dose-dependent positive inotropic effect on isolated rat hearts.
- The inotropic response to PrRP was not potentiated by inhibition of cAMP catabolism.
- Inhibition of protein phosphatase 1/2A (PP1/PP2A) with calyculin A enhanced the PrRP effect, while PP2A inhibition alone had no impact.
- Inhibition of protein kinase C alpha (PKC alpha) significantly amplified the inotropic response and phospholamban phosphorylation at Ser-16.
Conclusions:
- PrRP exerts a direct positive inotropic effect, establishing a novel role in cardiovascular regulation.
- The cardiac effects of PrRP are independent of the cyclic AMP (cAMP) pathway.
- Concurrent activation of PKC alpha and PP1 appears to suppress the cAMP-independent inotropic response to PrRP.
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