Residence Time of Polaprezinc (Zinc L-Carnosine Complex) in the Rat Stomach and Adhesiveness to Ulcerous Sites

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 ^^14 C-radioactivity in the gastric contents and gastric tissues were parallel to those of ^^65 Zn after oral administration of a mixture of ^^14 C-polaprezinc and ^^65 Zn-polaprezinc (^^14 C-, ^^65 Zn-polaprezinc) to rats. The gastric contents of ^^14 C-polaprezinc and ^^65 Zn-polaprezinc were greater than those of ^^14 C-L-carnosine and ^^65 ZnSO_4 . Mean residence times (MRT) of ^^14 C-polaprezinc and ^^65 Zn-polaprezinc in the stomach were almost the same (ca. 2 hr), and they were double those of ^^14 C-L-carnosine and ^^65 ZnSO_4 . In gastric tissues, the area under the concentration curves (AUC_0-8 hr ) of ^^14 C-polaprezinc and ^^65 Zn-polaprezinc were 1.7 times greater than those of ^^14 C-L-carnosine and ^^65 ZnSO_4 , respectively. After administration of ^^14 C-, ^^65 Zn-polaprezinc to rats with acetic acid-induced ulcers, ^^14 C and ^^65 Zn-radioactivities in the ulcerous sites were very similar and greater than those of ^^14 C-, ^^65 Zn-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.