Post‐natal changes inMCT1 expression in the forestomach of calves

Abstract

The monocarboxylate transporter 1 (MCT1) has been demonstrated to be involved in the transfer of short-chain fatty acids (SCFA) and/or their intraepithelial metabolites from the rumen to the blood. As MCT1 plays a role in SCFA transfer, it is assumed that SCFA are the main substrates influencing its expression. However, there are hints that MCT1 may also be expressed during the early life of the animal when SCFA are not released in the forestomach. To figure out whether MCT1 expression in the forestomach is influenced independently of SCFA during that period, we studied post-natal MCT1 expression immunohistochemically in the epithelia of omasum, atrium ruminis, saccus dorsalis ruminis, saccus ventralis ruminis and reticulum of calves born preterm and at term. The calves were nourished by colostrum or by milk-based formula diet. MCT1 could be found in all the forestomach compartments tested, even in preterm calves. The protein was mainly oriented to the luminal side in the immature epithelium 24 h after birth. Orientation to the blood side of the cells developed during the first 4 days after birth. In the rumen epithelia (but not in the other forestomach compartments tested), orientation of MCT1 to the blood side of the cells was paralleled by an increase in the overall expression rate during the first 4 days after birth. As lactate levels were very high directly after birth, a lactate-dependent substrate induction may have been the underlying mechanism. However, non-specific changes due to general differential processes might also be the cause. Both early upregulation of MCT1 and high blood lactate levels may provide the epithelia with lactate as energy source.

Differences in monocarboxylic acid transporter type 1 expression in rumen epithelium of newborn calves due to age and milk or milk replacer feeding

“…Similar to our findings, Pfannkuche et al. () did not find the differences in MCT1 protein expression between dorsal and ventral sac of rumen. Furthermore, those authors found substantial basal MCT1 protein expression in first day of calves' life, which increased during next 4 days although calves had no access to solid feed.…”

“…As forestomachs are not developed in newborn ruminants, the increase in MCT1 expression in the rumen epithelial cells within first weeks of calves' life is not surprising and supports the results of other studies (Kirat et al., ; Koho et al., ; Oba et al., ; Pfannkuche et al., ). For example, Oba et al.…”

“…As forestomachs are not developed in newborn ruminants, the increase in MCT1 expression in the rumen epithelial cells within first weeks of calves' life is not surprising and supports the results of other studies (Kirat et al, 2005;Koho et al, 2011;Oba et al, 2012;Pfannkuche et al, 2013). For example, Oba et al (2012) observed threefold increase in MCT1 mRNA expression between first and third week of calves' life, and Koho et al (2011) noticed 14 times higher MCT1 protein abundance in 2-week-old goats as compared to kids being 1 day old.…”

“…Furthermore, MCT1 may play different physiological role for rumen epithelium functions depending on the age of calves, as suggested by Pfannkuche et al. ().…”

“…Furthermore, a significant correlation between solid feed intake, SCFA concentration in the rumen and MCT1 protein expression, both in the dorsal and ventral sac of the rumen was shown, supporting an importance of solid feed intake for forestomachs development. On the other hand, some functional features of the rumen epithelium may develop independently of solid feed intake (Breves et al., ; Lane et al., ; Pfannkuche et al., ), and they may be affected by the type of liquid feed (milk or milk replacer) or amount of liquid feed consumed (Górka et al., ; Naeem et al., ).…”