Studies of the toxicological potential of tripeptides (L-valyl-L-prolyl-L-proline and L-isoleucyl-L-prolyl-L-proline):: III.: Single- and/or repeated-dose toxicity of tripeptides-containing Lactobacillus helveticus-fermented milk powder and casein hydrolysate in rats

The objective of these studies was to assess the toxicological potential of orally administered tripeptides in rats. The studies employed powdered L-valyl-L-prolyl-L-proline (VPP)- and L-isoleucyl-L-prolyl-L-proline (IPP)-containing test articles, including (1) powdered Lactobacillus helveticus-fermented milk (FM), (2) pasteurized casein hydrolysate (CH) generated by Aspergillus oryzae protease, and (3) synthesized VPP. All test articles were administered by oral gavage to male and female Sprague-Dawley rats. Specific goals of the single-dose and repeated-dose studies were to (1) identify doses that produce evidence of systemic and/or local (i.e., gastrointestinal) toxicity (e.g., lowest-observable-effect level [LOEL]); (2) estimate the maximally tolerated oral dose (MTD); and (3.) identify specific target organs for toxicity of these tripeptides. Single (loses of CH (2000 mg/kg), powdered FM (2000 or 4000 mg/kg), or VPP (40, 200, or 400 mg/kg) were administered 14 days prior to study termination. No treatment regimen caused either antemortem (gross observations, body weight, and food consumption parameters) or postmortem (necropsy) evidence of either systemic or local toxicity. In the repeated-dose study, powdered FM (0, 500, 1000, or 2000 mg/kg body weight [BW]/day) was administered by gastric gavage to male and female rats for 28 consecutive days. Antemortem evaluative parameters included gross observations, ophthalmic examinations, and clinical pathology (clinical chemistry, hematology, and urinalysis). Post mortem parameters included necropsy, determination of organ weights, and microscopic examination of major organs. There was neither in-life nor postmortem evidence that powdered FM administration caused physiological or toxicological changes. Under the conditions of these experiments, the single-dose LOEL of powdered FM, CH, and VPP were found to be greater than 4000, 2000, and 400 mg/kg, respectively. The results of the repeated-dose study do not support identification of a target organ for powdered FM toxicity. Similarly, there was no evidence to support establishment of either the LOEL or MTD; both being greater than 2000 mg/kg/day for up to 28 consecutive days.