Heart Cells Produce Opioid Peptides and Their Production Can Be Increased | Research

The takeaway

Adult rat heart muscle cells actively express opioid peptide genes, and this expression can be significantly increased by activating protein kinase C signaling pathways.

4-hour peak expression
Prodynorphin mRNA in cardiac myocytes peaked at 4 hours after protein kinase C activation

What the researchers found

Phorbol ester induced a concentration- and time-dependent increase in prodynorphin mRNA in cardiac myocytes, peaking at 4 hours and mediated through protein kinase C.

Why it matters

The discovery that the heart produces its own opioid peptides suggests a local cardioprotective system that may help the heart cope with stress, ischemia, or injury.

How the study worked

Adult rat ventricular cardiac myocytes were cultured with or without phorbol ester. Prodynorphin mRNA levels were measured over time and at varying concentrations, with protein kinase C inhibitors used to confirm the signaling pathway.

What this study cannot tell us

In vitro study using isolated rat heart cells stimulated with a pharmacological agent. The physiological conditions that would naturally trigger this response in the intact heart were not established.

How to read the evidence

Preliminary in vitro evidence from rat cardiac cells. Demonstrates a mechanism but physiological significance in the intact heart remains to be established.

When this study was published

Published in 1995, this is an early study establishing opioid peptide expression in cardiac tissue.

The bigger picture

This finding contributed to the understanding that opioid peptides have roles far beyond pain relief — they may serve as part of the heart's own protective signaling system during stress or damage.

Questions still open

Do cardiac opioid peptides play a protective role during heart attacks or ischemia?
Could enhancing cardiac dynorphin production offer cardioprotective benefits?

Common questions

Why does the heart produce opioid peptides?

The heart's local production of dynorphin-related opioid peptides likely serves a protective role. Opioid peptides can reduce cell damage during oxygen deprivation and may help regulate heart function during stress.

What is protein kinase C?

Protein kinase C (PKC) is an enzyme that activates other proteins by adding phosphate groups to them. It's involved in many cellular signaling pathways and can be activated by various stimuli including stress, hormones, and growth factors.

Read the original research

Phorbol ester regulation of opioid peptide gene expression in myocardial cells. Role of nuclear protein kinase.

The Journal of biological chemistry, 270(50), 30115-20

View on PubMed ↗

Citation

Ventura, C; Pintus, G; Vaona, I; Bennardini, F; Pinna, G; Tadolini, B. (1995). Phorbol ester regulation of opioid peptide gene expression in myocardial cells. Role of nuclear protein kinase.. The Journal of biological chemistry, 270(50), 30115-20.