Modification of spontaneous contractility of smooth muscle preparations from the bovine abomasal antrum by serotonin receptor agonists

Contractile Response of Bovine Lateral Saphenous Vein to Ergotamine Tartrate Exposed to Different Concentrations of Molecularly Imprinted Polymer

Ergot alkaloids, in their active isomeric form, affect animal health and performance, and adsorbents are used to mitigate toxicities by reducing bioavailability. Adsorbents with high specificity (molecularly imprinted polymers: MIP) adsorb ergot alkaloids in vitro, but require evaluation for biological implications. Using ex vivo myography, synthetic polymers were evaluated for effects on the bioactivity of ergotamine tartrate (ETA). Polymers were first evaluated using isotherms. Lateral saphenous veins were collected from 17 steers for four independent studies: dose response of ETA, adsorbent dose response, validation of pre-myograph incubation conditions and MIP/ non-molecularly imprinted polymer (NIP) comparison. Norepinephrine normalized percent contractile response to increasing ETA exhibited a sigmoidal dose response (max: 88.47 and log of the effective molar concentration (EC50) (-log [ETA]) of 6.66 ± 0.17 M). Although sample preparation time affected contractile response (p < 0.001), pre-myograph incubation temperature (39 vs. 21 °C, 1 h) had no effect (p > 0.05). Isothermal adsorption showed a maximum adsorption of 3.27E-008 moles·mg-1 and affinity between 0.51 and 0.57 mg (R²: 0.83-0.92) for both polymers, with no significant difference between polymers (p > 0.05). No significant differences in maximum inhibitory (p = 0.96) and IC50 responses (p = 0.163) between MIP and NIP were noticed. Normalized percent contraction could be predicted from the in vitro adsorption data (R² = 0.87, p < 0.01), for both polymers. These studies indicate that synthetic polymers are potentially effective adsorbents to mitigate ergot toxicity caused by ergot alkaloids, with little evidence of significant differences between MIP and NIP in aqueous media.

5-Hydroxytryptamine-4 receptor messenger ribonucleic acid levels and densities in gastrointestinal muscle layers from healthy dairy cows1

Serotonin (5-hydroxytryptamine, 5-HT) is involved in gastrointestinal tract (GIT) motor functions through binding to specific receptors located in the GIT walls. The objectives of the current study were to compare mRNA levels and binding sites of 5-HT(4) receptors (5-HTR(4)) in smooth muscle layers from the fundus abomasi, pylorus, ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of healthy dairy cows, and to verify whether mRNA and protein expression were correlated. Smooth muscle samples were prepared by scraping the mucosa and submucosa from full-thickness intestinal wall samples. The mRNA levels of 5-HTR(4) were measured by real-time PCR and expressed relative to those of the housekeeping gene glyceraldehyde phosphate dehydrogenase. Binding studies were performed using the 5-HTR(4) antagonist [(3)H]GR113808. The mRNA levels of 5-HTR(4) were affected (P < 0.05) by location along the GIT. The mRNA levels of 5-HTR(4) in the ELSC and the ileum were greater than in the PLAC (P = 0.05 and P = 0.07, respectively) but similar to those of all other locations. The competitive binding of [(3)H]GR113808 to suspended membranes from the fundus abomasi, pylorus, cecum, and ELSC was best fit by a 2-site receptor model, whereas it was best fit by a 1-site receptor model in the ileum and PLAC. The mRNA levels and numbers of 5-HTR(4) were not correlated (r = 0.14; P = 0.71). In conclusion, mRNA and binding sites for 5-HTR(4) are present in the smooth muscle layer of the entire GIT of dairy cows and may play a role with respect to motility. The effects of activation of this receptor subtype may be different among GIT locations due to differences in the amount of high- relative to low-affinity binding sites.

Distribution of mRNA coding for 5-hydroxytryptamine receptor subtypes in the intestines of healthy dairy cows and dairy cows with cecal dilatation-dislocation

OBJECTIVE

To investigate the distribution of mRNA coding for 7 subtypes of 5-hydroxytryptamine receptors (5-HTRs) in the intestines of healthy dairy cows and dairy cows with cecal dilatation-dislocation (CDD).

SAMPLE POPULATION

Full-thickness intestinal wall biopsy specimens were obtained from the ileum, cecum, proximal loop of the ascending colon, and external loop of the spiral colon (ELSC) of 15 cows with CDD (group 1) and 15 healthy dairy cows allocated to 2 control groups (specimens collected during routine laparotomy [group 2] or after cows were slaughtered [group 3]).

PROCEDURE

Amounts of mRNA coding for 7 subtypes of 5-HTRs (5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, and 5-HT4) were measured by quantitative real-time reverse transcriptase-PCR assay. Results were expressed as the percentage of mRNA expression of a housekeeping gene.

RESULTS

Expression of mRNA coding for 5-HTR1B, 5-HTR2B, and 5-HTR4 was significantly lower in cows with CDD than in healthy cows. For 5-HTR2B and 5-HTR4, significant differences between cows with CDD and control cows were most pronounced for the ELSC. Expression of mRNA for 5-HTR1D, 5-HTR1F, and 5-HTR2A was extremely low in all groups, and mRNA for 5-HTR1A was not detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Relative concentrations of mRNA coding for 5-HTR1B, 5-HT2B, and 5-HTR4 were significantly lower in the intestines of cows with CDD than in the intestines of healthy dairy cows, especially for 5-HT2B and 5-HTR4 in the ELSC. This supports the hypothesis that serotonergic mechanisms, primarily in the spiral colon, are implicated in the pathogenesis of CDD.

Expression of Messenger RNA Coding for 5-HT Receptor, Alpha and Beta Adrenoreceptor (Subtypes) during Oestrus and Dioestrus in the Bovine Uterus

Serotoninergic and adrenergic receptors (5-HTR and AR) are involved in the regulation of uterine contractility. The objective of this study was to compare mRNA levels of 5-HTR(1A), 5-HTR(1B), 5-HTR(1D), 5-HTR(1F), 5-HTR(2A), 5-HTR(2B), 5-HTR(2C), 5-HTR(4) and alpha(1A), alpha(1B), alpha(1D), alpha(2AD), alpha(2B), alpha(2C), and beta(1), beta(2), beta(3)-AR in oestrus and dioestrus, and at three uterine locations (tip, middle and base) using quantitative real-time polymerase chain reaction. Uterine specimens consisting of endometrium and myometrium including vessels and serosa were collected from cows in oestrus (n = 10) and dioestrus (n = 15) respectively. Levels of 5-HTR and AR mRNA were expressed relative to the geometric mean of ribosomal RNA (18S), ubiquitin and glyceraldehyde phosphate dehydrogenase by the mean values of geNorm algorithm. 5-HTR(1A), 5-HTR(2C) and beta(3)-AR mRNA could not be detected in uterine tissues. The mRNA levels of 5-HTR(1F) and 5-HTR(2B) were lower (P < 0.05), but of 5-HTR(4) were higher (P < 0.05) in oestrus than in dioestrus. The mRNA levels of alpha(1A)-AR, alpha(2AD)-AR, alpha(2B)-AR were lower (P < 0.05), but of alpha(2C)-AR and beta(2)-AR were higher (P < 0.05) in oestrus than dioestrus. The mRNA levels of 5-HTR(1B) and 5-HTR(1D) (oestrus) and of alpha(2AD)-AR (dioestrus) differed among uterine locations (base > middle > tip; P < 0.05). The mRNA expression of 5-HTR and AR (subtypes) in bovine uterus was associated with cycle activity and varied according to uterine location. Additional studies on protein level will be carried out in order to elucidate the role of these receptor families on uterine contractility, which may then help to clarify clinical relevance.

Distribution of mRNA that codes for 5-hydroxytryptamine receptor subtypes in the gastrointestinal tract of dairy cows

OBJECTIVE

To describe the distribution of mRNA that codes for 8 subtypes of 5-hydroxytryptamine receptors (5-HTRs) 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 5-HTR subtypes (5-HTR1A. 5-HTR1B, 5-HTR1D, 5-HTR1F, 5-HTR2A, 5-HTR2B, 5-HTR2C, and 5-HTR4) in the bovine digestive tract 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 relative mRNA concentrations for 5-HTR were low (range, 0% to 1.32% of GAPDH), and mRNA that codes for 5-HTR1A was not detected. In the abomasum, mRNA expression was highest for 5-HTR1B and 5-HTR2B, followed by subtypes 1F 2A, 1D, and 4, whereas 5-HTR2C was not detected. In intestinal samples, concentrations of subtypes 1B, 2B, and 4 were highest, followed by 1D, 1F, 2A, and 2C. Relative concentrations of mRNA that code for 5-HTR2A were significantly higher in the abomasum than the intestines, but lower for 5-HTR2B, 5-HTR2C, and 5-HTR4.

CONCLUSIONS AND CLINICAL RELEVANCE

Relative concentrations of mRNA that code for 5-HTRs differ among locations in the gastrointestinal tract of cattle. Understanding differences in the distribution of 5-HTRs in healthy cattle and cattle with gastrointestinal tract disease may lead to improved therapeutic approaches for abomasal and cecal motility disorders.