Serum concentrations of L-lysine decreased by sialoadenectomy in the rat

Abstract

We investigated participation of salivary glands in formation of taste preference by analyzing preferences for (48hr-two bottle choice test) and concentrations of serum amino acids in rats with removal of the submandibular and sublingual glands, and L-lysine (lysine) deficient rats. Intact control animals preferred L-arginine solution to lysine solution and water whereas sialoadenectomized animals and lysine deficient animals preferred lysine solution to L-arginine solution and water. Amino-acid analysis showed that serum concentrations of lysine and L-isoleucine in sialoadenectomized animals, being approximately equal to those in lysine deficient animals, were significantly lower than those in controls. Even after oral administration of 25% skim milk, lysine levels were low in sialoadenectomized animals compared with in controls over at least two hours. These results suggest that even when animals are fed lysine sufficient diet, sialoadenectomy brings about lysine deficiency, where taste for amino acids changes. This study also showed the presence of at least three lysine-binding (60-67 kDa) proteins in submandibular-sublingual saliva. The lack of these proteins could be attributed to lysine deficiency caused by sialoadenectomy. [Jpn J Physiol 54 Suppl:S232 (2004)]