Localization of urea transporter B in the developing bovine rumen

• Published in: Animal Nutrition Vol. 10; pp. 216 - 222
• Main Authors: Zhong, Chongliang, Lyons, Tamsin, Heussaff, Orla, Doyle, Evelyn, O'Hara, Eoin, Waters, Sinead M., Kenny, David, Stewart, Gavin S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2022; KeAi Publishing; KeAi Communications Co., Ltd
• Subjects: Bovine; Development; Immunolocalization; Rumen; Short Communication; UT-B; Immunolocalization; Development; Rumen; UT-B; Bovine
• ISSN: 2405-6545; 2405-6383
• DOI: 10.1016/j.aninu.2022.03.006

Urea nitrogen secreted from blood to rumen is a crucial factor shaping the symbiotic relationship between host ruminants and their microbial populations. Passage of urea across rumen epithelia is facilitated by urea transporter B (UT-B), but the long-term regulation of these proteins remains unclear. As ruminal function develops over a period of months, the developing rumen is an excellent model with which to investigate this regulation. Using rumen epithelium samples of calves from birth to 96 d of age, this study performed immunolocalization studies to localize and semi-quantify UT-B protein development. As expected, preliminary experiments confirmed that ruminal monocarboxylate transporter 1 (MCT1) short chain fatty acid transporter protein abundance increased with age (P < 0.01, n = 4). Further investigation revealed that ruminal UT-B was present in the first few weeks of life and initially detected in the basolateral membrane of stratum basale cells. Over the next 2 months, UT-B staining spread to other epithelial layers and semi-quantification indicated that UT-B abundance significantly increased with age (P < 0.01, n = 4 or 6). These changes were in line with the development of rumen function after the advent of solid feed intake and weaning, exhibiting a similar pattern to both MCT1 transporters and papillae growth. This study therefore confirmed age-dependent changes of in situ ruminal UT-B protein, adding to our understanding of the long-term regulation of ruminal urea transporters.