Genesis of Esophageal Parakeratosis and Histologic Changes in the Testes of the Zinc-deficient Rat and Their Reversal by Zinc Repletion

Abstract

A histologic study of the early changes in the esophagus and testes was made in the zinc-deficient rat. Cellular changes in these tissues were described in 2 experiments comprising a total of 72 animals, extending to 44 days in the first study and 45 days in the second. In the first study, rats were fed a zinc-deficient diet (0.5 ppm) and compared with pair-fed and ad libitum controls fed the same diet supplemented with 30 ppm of zinc. The earliest changes in the esophagus of hyperkeratosis and parakeratosis were observed on day 16 of the experiment. In the testes of the zinc-deficient animals fed their diet for 23 days, there was a decreased number of spermatids with many seminiferous tubules appearing immature in comparison with those of the pair-fed controls. In zinc deficiency of the rat the transformation of spermatids to spermatozoa is inhibited, which appears to be the earliest histologic change in spermiogenesis. The animals in the second study were offered a low zinc diet (2.5 ppm) for 10 days, then fed a zinc-deficient diet (0.5 ppm) for 13 days, and were compared with pair-fed controls. Histology of the esophagi of 4 rats fed the low zinc diet for 10 days was similar to that of the pair-fed controls. Eleven deficient animals were repleted with 1 mg of zinc (ZnSO₄·7H₂O) by intraperitoneal injection in the 2 experiments. In the first study, 3 rats were repleted for 3, 12, and 18 hours, respectively, for histology of the esophagi, and 2 rats were repleted for 14 days for histology of the testes. In the second, 6 rats were repleted for 24 hours and showed complete keratinization of their esophagi, compared with the progressive recovery of the lesion in the 3 rats of the first study. No recovery was observed in the testes. Zinc determinations from pooled serum of 15 rats in the first study representing the deficient, repleted, pair-fed and ad libitum groups had values from 82.5 to 97.5 µg/100 ml in the repleted and deficient, and 123 to 192 µg/100 ml in the controls.