Distribution of mRNA that codes for subtypes of adrenergic receptors in the gastrointestinal tract of dairy cows.

Objective--To describe the distribution of mRNA that codes for 9 subtypes of adrenergic receptors in the digestive tract of dairy cows. Sample Population--Fresh full-thickness wall specimens from the abomasum (fundus, corpus, and antrum), ileum, cecum, proximal loop of ascending colon, and 4 locations of the spiral colon collected from 10 healthy cows at slaughter. Procedure--Concentrations of mRNA that code for 9 subtypes of adrenergic receptors in the bovine gastrointestinal tract (α1A, α1B, α1D α2AD, α2B, α2C, β1, β2 and β3) were measured by use of a quantitative real-time reverse transcription-polymerase chain reaction assay. Results were reported in relation to mRNA expression of the housekeeping gene glyceraldehyde phosphate dehydrogenase (GAPDH). Results--Mean mRNA contents of adrenergic receptors in the bovine digestive tract were low (range, 0.00006% to 5.04% of GAPDH). Distribution of receptor subtypes was similar in all tissues, with lowest expression of α1D receptors, followed by α2B, α2C, β3, α1B, α1A, β1 and β2 in the abomasum, whereas α2AD and β2 in the intestines were highest. In comparison with the intestines, relative concentrations of mRNA for receptors β2 and β3 were significantly lower in the abomasum. Conclusions and Clinical Relevance--Relative concentrations of mRNA that code for adrenergic receptors differed among receptor subtypes and among locations in the bovine gastrointestinal tract. Comparison of these values established in healthy cattle with results for cows with motility disorders, such as abomasal displacement and cecal dilatation, may lead to improved... [ABSTRACT FROM AUTHOR]