Urea Transport across the Rumen Epithelium is Electrically Silent and Modulated by Changes in pH

This paper had been presented for promotion at the university of Khartoum to get the full text please contact the other at abdounn@yahoo.comIn ruminants, recycling of urea has been established as a key element in the nitrogen balance of these animals (Fig 1). Secretion of urea by the rumen epithelium is linearly related to the rumen-blood concentration gradient and has been studied both in vivo and in vitro (Simmonet et al., 1957, Gärtner et al., 1961; v. Engelhardt und Nickel, 1965; Houpt and Houpt, 1968), but the route is unclear. Classically, transport via non-specific diffusion was assumed. But recently, UT mRNA and protein have been demonstrated (Ritzhaupt et al., 1997; 1998; Marini et al., 2004 ) with corresponding staining in membranes of all epithelial layers of the bovine rumen with the exception of the stratum corneum (Stewart et al. (2005). Since SGLT1 has been demonstrated in the rumen (Aschenbach et al., 2000), substitution for glucose in this (electrogenic) transporter also appears a possibility (Leung et al., 2000). In this study, urea fluxes were studied under varying conditions in order to find out more about the transport of urea across the rume