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Vasoactive intestinal peptide stimulates proenkephalin A mRNA expression in bovine adrenal chromaffin cells
1Department of Biochemistry, University of Melbourne, Parkville, Vic., Australia.
Abstract:
The effects of vasoactive intestinal peptide (VIP) and substance P (SP) on the amount of proenkephalin A (ProEnk A) mRNA in cultures of bovine adrenal chromaffin cells were examined. Exposure of chromaffin cells to 5 microM VIP for 24 h produced a significant elevation in ProEnk A mRNA. The stimulatory effect of VIP could be abolished by the presence of the calcium channel blocker D600 or actinomycin D but was not affected by the nicotinic antagonist hexamethonium. The results suggest that VIP may induce transcription of ProEnk A mRNA by a Ca2+-dependent, non-cholinergic mechanism. By contrast, SP (5 microM) had no effect on the amount of ProEnk A mRNA. Since VIP is found in nerve terminals and the ganglion cells within the adrenal medulla, this peptide could be an endogenous regulator of adrenal enkephalin gene expression.
Insights
Vasoactive intestinal peptide (VIP) significantly increases proenkephalin A mRNA in adrenal cells. This VIP effect is calcium-dependent and non-cholinergic, suggesting VIP regulates enkephalin gene expression.
Area of Science:
- Neuroendocrinology
- Molecular biology
- Cellular signaling
Background:
- Adrenal chromaffin cells synthesize and release catecholamines and peptides.
- Enkephalins are endogenous opioid peptides involved in stress response and pain modulation.
- Vasoactive intestinal peptide (VIP) and substance P (SP) are neuropeptides found in the adrenal medulla.
Purpose of the Study:
- To investigate the effects of VIP and SP on proenkephalin A (ProEnk A) mRNA levels in bovine adrenal chromaffin cells.
- To elucidate the signaling pathways involved in VIP-induced regulation of ProEnk A gene expression.
Main Methods:
- Primary cultures of bovine adrenal chromaffin cells were treated with VIP or SP.
- Proenkephalin A mRNA levels were quantified using molecular biology techniques.
- The roles of calcium channels and transcription were assessed using specific inhibitors (D600, actinomycin D) and nicotinic antagonists (hexamethonium).
Main Results:
- VIP (5 microM) significantly increased ProEnk A mRNA levels after 24 hours of exposure.
- The stimulatory effect of VIP was blocked by the calcium channel blocker D600 and actinomycin D, indicating a Ca2+-dependent transcriptional mechanism.
- SP (5 microM) had no significant effect on ProEnk A mRNA levels.
- The VIP effect was not inhibited by the nicotinic antagonist hexamethonium, suggesting a non-cholinergic pathway.
Conclusions:
- VIP acts as a potent stimulator of proenkephalin A gene expression in adrenal chromaffin cells.
- VIP-induced ProEnk A mRNA transcription is mediated by a calcium-dependent, non-cholinergic mechanism.
- VIP, present in the adrenal medulla, may function as an endogenous regulator of enkephalin synthesis in the adrenal gland.