Search

A nitric oxide synthase (NOS) inhibitor, NG-nitro-L -arginine methyl ester (L-NAME), was given to zinc-deficient (ZD) rats to determine whether it prevents the intestinal damage usually observed under these conditions. Weanling male rats were given free access to a ZD diet (2 mg zinc/kg), whereas control rats including pair-fed (PF) and ad libitum consumption (AL) groups were given a zinc-supplemented (50.8 mg zinc/kg) diet for 4 wk. Half of the ZD rats received L-NAME (0.3 g/L in drinking water) for 3 wk starting at the wk 2 of the deficient period. Plasma zinc concentration in ZD rats was significantly lower (P < 0.05) than that of AL and PF rats. Administration of L-NAME did not alter this concentration. Intestinal zinc concentration did not differ among groups. However, metallothionein-1 (MT-1) mRNA level was significantly lower in the intestine of ZD rats than in AL or PF rats. Treatment of ZD rats with L-NAME did not affect this level. Intestinal microvascular permeability evaluated by Evans blue showed significantly higher extravasation in ZD rats than in AL rats, whereas L-NAME administration inhibited the extravasation. Expression of inducible NOS mRNA was observed in intestine of ZD but not of AL or PF rats, and there was no significant difference between ZD rats, regardless of L-NAME treatment. The activity ratio of inducible NOS to total NOS in ZD rats not receiving L-NAME was significantly higher than that in AL rats or ZD rats treated with L-NAME (P < 0.05). The number of apoptotic-positive and goblet cells in intestinal villi was significantly higher in ZD rats compared with AL or PF rats. L-NAME administration in ZD rats reversed this effect. These results indicate that inhibition of NOS ameliorates zinc deficiency-induced intestinal damage in rats. KEY WORDS: nitric oxide synthase inhibitor; apoptosis; goblet cell hyperplasia; zinc deficiency; intestine; rats

This study investigated whether interleukin-1[Alpha]-induced metallothionein gene expression is affected by zinc deficiency. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) or a zinc-supplemented diet [50.8 mg zinc/kg; controls for the diet included pair-fed (PF) and ad libitum consumption groups (AL)] for 4 wk. All rats except those that served as controls for interleukin-l[Alpha] administration, (injected with vehicle and killed at 0 h) were then injected subcutaneously with interleukin-1[Alpha] (2 x [10.sup.7] units/kg body wt) and killed at 3, 6, 12, 24 and 72 h after the injection. Compared with AL and/or PF rats, zinc depletion significantly reduced zinc concentrations in plasma and liver but not in kidney or intestine, and significantly reduced hepatic, renal, and intestinal metallothionein-1 mRNA levels analyzed by competitive reverse transcription-polymerase chain reaction (RT-PCR). Interleukin-1[Alpha] injection reduced plasma zinc concentration and enhanced liver zinc concentration, but did not affect zinc levels in kidney or intestine. Metallothionein-1 mRNA was significantly elevated by interleukin-1[Alpha] in liver, kidney and intestine of all groups; the levels in liver and kidney of ZD rats 6 h after the injection were significantly higher than those of AL or PF rats. Liver metallothionein protein levels were enhanced after interleukin-1[Alpha] injection in both AL and ZD rats. Semiquantitative RT-PCR revealed significantly higher hepatic levels of interleukin-1 receptor type-I mRNA in ZD rats than in AL and PF rats but no differences in renal or intestinal tissues among groups before interleukin-l[Alpha] challenge. In conclusion, zinc deficiency induces upregulation of metallothionein-1 gene expression in response to interleukin-l[Alpha] challenge in rats. KEY WORDS: interleukin-1; metallothionein; mRNA expression; zinc deficiency; rats

Synthesis of inducible nitric oxide synthase (iNOS) in the intestine may result in local tissue damage. We investigated whether a challenge with interleukin-1[Alpha] could give rise to intestinal iNOS expression and diarrhea in rats of differing zinc status. Weaning male rats were fed a zinc-deficient (ZD) diet (2 mg zinc/kg) for 4 wk to induce zinc deficiency or a zinc-supplemented diet [50.8 mg zinc/kg; controls, including pair-fed (PF) and ad libitum (AL) consumption groups], and then subcutaneously injected with interleukin-1[Alpha] (2 x [10.sup.7] units/kg body wt). Without the interleukin-1[Alpha] challenge, ZD rats had significantly lower plasma zinc concentration than the other groups. Intestinal metallothionein-1 mRNA abundance was lower in ZD rats than in AL rats. iNOS was expressed in the intestine of ZD rats but not in the others. None of the rats experienced diarrhea during the feeding period. Interleukin-1[Alpha] led to a reduction in plasma zinc concentration, enhancement in intestinal metallothionein-1 mRNA levels, and expression of the intestinal iNOS gene in all groups. However, the abundance of iNOS mRNA was significantly higher in ZD rats than in the other groups. The presence of iNOS protein was demonstrated by immunohistochemical staining in the intestine of ZD rats that had been treated with interleukin-1[Alpha] 12 h earlier. In addition, diarrhea occurred in most of the ZD rats and some of the PF rats but not in AL rats after interleukin-1[Alpha] treatment. We conclude that ZD rats respond to interleukin-1[Alpha] challenge more severely than controls, reflected by a more marked and prolonged iNOS expression and a greater incidence of diarrhea. KEY WORDS: interleukin-1[Alpha]; nitric oxide synthase; metallothionein; zinc; rats; diarrhea