ABSTRACT-Polaprezinc, an insoluble zinc complex of L-carnosine, exhibits anti-ulcer effects by acting directly on mucosal lesions. The disposition of polaprezinc in the stomach was studied to clarify the usefulness of its structure as an insoluble complex. The time courses of 14C-radioactivity in the gastric contents and gastric tissues were parallel to those of 65Zn after oral administration of a mixture of 14C-polaprezinc and 65Zn-polaprezinc (14C-, 65Zn-polaprezinc) to rats. The gastric contents of '4C-polaprezinc and 65Zn-polaprezinc were greater than those of 14C-L-carnosine and 65ZnSO4. Mean residence times (MRT) of 14C-polaprezinc and 65Zn-polaprezinc in the stomach were almost the same (ca. 2 hr), and they were double those of 14C-L-carnosine and 65ZnSO4. In gastric tissues, the area under the concentration curves (AUCO_8 hr) of 14C-polaprezinc and 65Zn-polaprezinc were 1.7 times greater than those of '4C-L-carnosine and 65ZnSO4i respectively. After administration of 14C-, 65Zn-polaprezinc to rats with acetic acid-induced ulcers, 14C and 65Zn-radioactivities in the ulcerous sites were very similar and greater than those of '4C-, 65Zn -polaprezinc dissolved in acid. In conclusion, polaprezinc is retained in the stomach longer and adheres to the ulcerous sites more than zinc or L-carnosine. The characteristics of this compound may arise from its insolubility and contribute to its strong pharmacological action.

No abstract

No abstract

The disposition of polaprezinc in the rat gastrointestinal tract was studied by a double tracer method using [14C]- and [65Zn]polaprezinc. At 0.5 h after oral administration of [14C]-,[65Zn]polaprezinc to rats, the 14C-radioactivity in the gastric contents was comparable with the 65Zn-radioactivity. However, a significant difference was observed in the time course of changes in gastric contents between 14C- and 65Zn-radioactivity over 1 h after administration, indicating that polaprezinc existed in complex form at 0.5 h after administration and was dissociated to L-carnosine and zinc in the gastrointestinal tract as a function of time. The adhesion of zinc to stomach mucosa after oral administration of polaprezinc to rats was significantly increased by treatment with cimetidine. These results suggest that the adhesion of zinc to gastric tissues is increased by inhibiting the dissociation of polaprezinc, and that H2-receptor antagonists, such as cimetidine, may increase anti-ulcer effects of polaprezinc.