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Messenger RNAs for neurokinin and histamine receptor subtypes in isolated canine colonic crypts
I Khan1, N Lapierre, P K Rangachari
1Dept. Medicine, McMaster University, Hamilton, Ont., Canada.
Abstract:
Functional subtyping of neurokinin and histamine receptors on the canine proximal colon suggested that different receptors were involved in mediating the neural and non-neural effects on ion transport. If the non-neural effects involved direct stimulation of the transporting epithelial cells, mRNA for specific receptor subtypes should be present in colonic crypt cells. Pharmacological data predicted that RNA from such cells would include mRNAs for neurokinin (NK-1) and histamine (H1 and H2) receptors but not for NK-2 or NK-3 receptors. Using published sequences for the above receptors and reverse-transcription polymerase chain reaction, we have noted that isolated canine colonic crypts had mRNA for NK-1 and NK-2 receptors but not for NK-3 receptors. Messenger RNAs for both H1 and H2 receptors were present. The muscularis mucosa and submucosal plexuses had mRNAs for NK-1, NK-3, H1 and H2 receptors but not for NK-2 receptors. The circular and longitudinal muscles expressed mRNA for all three neurokinin and both histamine receptors. Messenger RNA levels for the alpha-1 isoform of the catalytic subunit of the sodium pump were higher in crypts and lower in muscularis mucosa and muscle preparation. Thus these observations provide further evidence for the existence of different receptor subtypes in the canine colon.
Insights
This study investigated neurokinin (NK) and histamine receptor expression in canine colon crypts and muscle layers. Findings reveal distinct receptor subtypes in different colon tissues, impacting ion transport mechanisms.
Area of Science:
- Gastroenterology
- Molecular Biology
- Pharmacology
Background:
- Neurokinin (NK) and histamine receptors play roles in canine proximal colon function.
- Previous studies suggested different receptors mediate neural and non-neural ion transport effects.
- The presence of specific receptor subtypes in colonic crypt cells was hypothesized for non-neural effects.
Purpose of the Study:
- To determine the presence and distribution of neurokinin (NK-1, NK-2, NK-3) and histamine (H1, H2) receptor messenger RNAs (mRNAs) in different canine proximal colon tissues.
- To investigate the expression of the alpha-1 isoform of the sodium pump catalytic subunit mRNA.
- To provide evidence for distinct receptor subtypes in the canine colon.
Main Methods:
- Isolation of canine colonic crypts, muscularis mucosa, submucosal plexuses, and muscle preparations.
- Reverse-transcription polymerase chain reaction (RT-PCR) to detect specific receptor mRNAs.
- Quantification of messenger RNA levels for the alpha-1 isoform of the sodium pump.
Main Results:
- Canine colonic crypts expressed mRNA for NK-1 and NK-2 receptors, but not NK-3. Both H1 and H2 receptor mRNAs were present.
- Muscularis mucosa and submucosal plexuses showed mRNA for NK-1, NK-3, H1, and H2 receptors, but not NK-2.
- Muscles expressed mRNA for all three neurokinin and both histamine receptors. Sodium pump alpha-1 isoform mRNA levels were higher in crypts and lower in muscle tissues.
Conclusions:
- The distribution of neurokinin and histamine receptor subtypes varies across different layers of the canine colon.
- These findings support the existence of distinct receptor subtypes in the canine colon, contributing to differential ion transport.
- The differential expression of the sodium pump alpha-1 isoform suggests layer-specific functional roles.