Increased methionine synthetase activity in zinc-deficient rat liver

To study the effect of zinc deficiency on folate metabolism, three groups of male Sprague-Dawley rats (zinc deficient (ZD), restricted-fed (RF + Zn), and ad libitum-fed control (control] were given a semipurified 25% egg white protein diet. The ZD group received less than 10.3 nmol zinc/g of diet, while the RF + Zn and control groups were given 1620 nmol zinc/g of diet. After 6-7 weeks of feeding, severe zinc deficiency developed in ZD rats. Hepatic methionine synthetase activity was increased in the ZD group compared to both the RF + Zn and control groups, but hepatic 5,10-CH2-H4folate reductase activity was similar in all groups. This increased methionine synthetase activity found in zinc-deficient rats might induce secondary alterations in folate metabolism. These changes include significantly lowered plasma folate levels, decreased 5-CH3-H4folate in liver, and increased rates of histidine and formate oxidation. The latter two findings suggest that the available non-5-CH3-H4folate is increased in zinc deficiency.     

Folate and homocysteine metabolism in copper-deficient rats.

To investigate the effect of copper deficiency on folate and homocysteine metabolism, we measured plasma, red-cell and hepatic folate, plasma homocysteine and vitamin B-12 concentrations, and hepatic methionine synthase activities in rats. Two groups of male Sprague-Dawley rats were fed semi-purified diets containing either 0. 1 mg (copper-deficient group) or 9.2 mg (control group) of copper per kg. After 6 weeks of dietary treatment, copper deficiency was established as evidenced by markedly decreased plasma and hepatic copper concentrations in rats fed the low-copper diet. Plasma, red-cell, hepatic folate, and plasma vitamin B-12 concentrations were similar in both groups, whereas plasma homocysteine concentrations in the copper-deficient group were significantly higher than in the control group (P<0.05). Copper deficiency resulted in a 21% reduction in hepatic methionine synthase activity as compared to the control group (P<0.01). This change most likely caused the increased hepatic 5-methyltetrahydrofolate and plasma homocysteine concentrations in the copper-deficient group. Our results indicate that hepatic methionine synthase may be a cuproenzyme, and plasma homocysteine concentrations are influenced by copper nutriture in rats. These data support the concept that copper deficiency can be a risk factor for cardiovascular disease.     

Dietary zinc deficiency decreases plasma concentrations of vitamin E

Experiments were conducted to examine the effects of dietary zinc (Zn) upon plasma vitamin E (E) concentrations to test the hypothesis that there may be a significant dietary interaction between these two nutrients. Weanling female Sprague-Dawley rats were fed diets that were (i) Zn-deficient (less than 0.9 micrograms Zn/g diet) ad libitum; (ii) Zn-adequate (50.9 micrograms Zn/g diet), pair-fed to the Zn-deficient group; and (iii) Zn-adequate (50.9 micrograms Zn/g diet) ad libitum. Plasma E in Zn-deficient animals (4.02 +/- 1.20 micrograms/ml) was significantly reduced (P less than or equal to 0.05) compared with results in both Zn-adequate pair-fed (9.21 +/- 0.70 micrograms/ml) and Zn-adequate ad libitum-fed (9.47 +/- 0.90 micrograms/ml) animals. Zn deficiency in this model system also resulted in significant (P less than or equal to 0.05) reductions in femur and plasma Zn concentrations as well as in plasma retinol, plasma triglyceride, and plasma cholesterol concentrations. Plasma albumin and total plasma protein concentrations were normal in Zn-deficient animals. With dietary Zn deficiency, the decrease in plasma E appeared to be out of proportion to associated decreases in plasma triglyceride and plasma cholesterol concentrations. Since E is associated with plasma lipoproteins, these data suggest that lipid and/or E malabsorption may be a consequence of Zn deficiency. In response to increased dietary intake of E, increments of plasma E were lower in Zn-depleted than in Zn-adequate, pair-fed animals. These findings suggest that dietary Zn deficiency possibly may increase the nutritional requirement for E necessary to maintain adequate plasma concentrations.     

Zinc-deficient rats have more limited bone recovery during repletion than diet-restricted rats

The objective of this study was to investigate the effects of dietary zinc deficiency and diet restriction on bone development in growing rats, and to determine whether any adverse effects could be reversed by dietary repletion. Weanling rats were fed either a zinc-deficient diet ad libitum (ZD; <1 mg zinc/kg) or nutritionally complete diet (30 mg zinc/kg) either ad libitum (CTL) or pair-fed to the intake of the ZD group (DR; diet-restricted) for 3 weeks (deficiency phase) and then all groups were fed the zinc-adequate diet ad libitum for 3, 7, or 23 days (repletion phase). Excised femurs were analyzed for bone mineral density (BMD) using dual-energy x-ray absorptiometry, and plasma was analyzed for markers of bone formation (osteocalcin) and resorption (Ratlaps). After the deficiency phase, ZD had lower body weight and reduced femur BMD, zinc, and phosphorus concentrations compared with DR; and these parameters were lower in DR compared with CTL. Femur calcium concentrations were unchanged among the groups. Reduced plasma osteocalcin in ZD and elevated plasma Ratlaps in DR suggested that zinc deficiency limits bone formation while diet restriction accelerates bone resorption activity. After 23 days of repletion, femur size, BMD, and zinc concentrations remained lower in ZD compared with DR and CTL. Body weight and femur phosphorus concentrations remained lower in both ZD and DR compared with CTL after repletion. There were no differences in plasma osteocalcin concentrations after the repletion phase, but the plasma Ratlaps concentrations remained elevated in DR compared with CTL. In summary, both ZD and DR lead to osteopenia during rapid growth, but the mechanisms appear to be due to reduced modeling in ZD and higher turnover in DR. Zinc deficiency was associated with a greater impairment in bone development than diet restriction, and both deficiencies limited bone recovery during repletion in growing rats.     

Renal metallothionein responds rapidly and site specifically to zinc repletion in growing rats

Metallothionein (MT) is important for heavy metals and free radical protection in the kidney. MT is responsive to zinc and primarily localized within the renal cortex. However, site-specific renal responses to dietary zinc repletion are understudied. The objective of this study was to examine the effects of dietary zinc deficiency and repletion on renal MT concentration and immunolocalization in rats. Weanling male Sprague Dawley rats were randomly assigned to either a zinc-deficient, zinc control, or pair-fed to zinc-deficient group. Half of the zinc-deficient and pair-fed rats were repleted with the control diet ad libitum for an additional 24 h. Renal tissue samples were assessed for total zinc, MT concentrations and MT immunostaining. Dietary zinc deficiency reduced renal zinc and MT concentrations, and attenuated intensity and localization of MT. Dietary zinc repletion for 24 h restored renal zinc and MT concentrations, the latter primarily in the proximal convoluted tubules of the cortex. Concentrations of renal MT, but not zinc, were elevated by diet restriction and MT (μg/mg protein) and partially normalized by 24 h diet repletion. In conclusion, renal MT modification due to zinc deficiency or diet restriction can be rapidly normalized in a site-specific manner with normal dietary zinc intake. The results support a role for MT in kidney homeostasis, in particular at the level of the proximal tubules in the cortex. The speed of MT repletion may have clinical implications for dietary zinc in the treatment of acute and chronic renal pathology due to toxins and free radicals.     

The isoelectric fractionation of hen''s-egg ovotransferrin

1. ATP sulphurylase was assayed in various organs from vitamin A-deficient and pair-fed control rats at different stages of deficiency. Activity decreased slightly in the liver and markedly in the adrenal gland. Striking differences in liver activity were observed between pair-fed control and ad libitum-fed animals. This observation suggested that diet (apart from vitamin A) strongly influenced the activity of ATP sulphurylase. 2. Total starvation caused a severe decrease in activity in liver within 48hr. This was due to a lack of protein intake. 3. By feeding groups of vitamin A-deficient and pair-fed control rats on a diet containing 80% protein, the specific activity of the liver ATP sulphurylase was maintained in the pair-fed control group at the normal level of an ad libitum-fed rat, whereas it decreased by 25% (statistically significant at P<0.01) in the deficient rat. On a 20%-protein diet, there were no significant differences between vitamin A-deficient and pair-fed control rats. These relationships held also for enzyme activity expressed per g. of liver, per total liver and per g. of DNA. There were no differences in liver protein or DNA concentration between vitamin A-deficient and control rats on either protein intake. 4. Control rats on a 20%-protein diet had liver specific enzyme activities about one-half of those in control rats on an 80%-protein diet, as well as lower liver protein concentrations. 5. It is concluded that, when the effect of protein deprivation on ATP sulphurylase is separated from the effect of vitamin A deficiency, a lowering of the enzyme activity caused by the vitamin deficiency is demonstrable.     

Dietary zinc restriction in rats alters antioxidant status and increases plasma F2 isoprostanes

Approximately 12% of Americans do not consume the estimated average requirement for zinc and could be at risk for zinc deficiency. Since zinc has proposed antioxidant function, inadequate zinc consumption may lead to an enhanced susceptibility to oxidative stress through several mechanisms, including altered antioxidant defenses. In this study, we hypothesized that dietary zinc restriction would result in lower antioxidant status and increased oxidative damage. We fed weanling Sprague-Dawley rats (n=12 per group) a zinc-adequate (50 mg/kg of zinc) diet, a zinc-deficient (<0.05 mg/kg of zinc) diet or a pair-fed diet for 3 weeks and then assessed their antioxidant status and oxidative stress parameters. Rats were zinc deficient as indicated by a significant (P<.05) reduction in body weight (49%) and 19% lower (P<.05) hepatic zinc (20.6+/-2.1 mg/kg) as compared with zinc-adequate rats (24.6+/-2.2 mg/kg). Zinc deficiency resulted in elevated (P<.05) plasma F(2) isoprostanes. Zinc deficiency-mediated oxidative stress was accompanied by a 20% decrease (P<.05) in the ferritin-reducing ability of plasma assay and a 50% reduction in plasma uric acid (P<.05). No significant change in plasma ascorbic acid or in plasma alpha-tocopherol and gamma-tocopherol was observed. However, hepatic alpha-tocopherol and gamma-tocopherol concentrations were decreased by 38% and 27% (P<.05), respectively, as compared with those in zinc-adequate rats. Hepatic alpha-tocopherol transfer protein levels were unaltered (P>.05) by zinc deficiency, but cytochrome P450 (CYP) 4F2 protein levels were elevated (P<.05) as compared with those in zinc-adequate rats. Collectively, zinc deficiency increased oxidative stress, which may be partially explained by increased CYP activity and reductions in hepatic alpha-tocopherol and gamma-tocopherol and in plasma uric acid.     

In vivo effects of zinc deficiency on calmodulin concentrations in selected rat tissues

Two groups of male Sprague-Dawley rats, one fed zinc-deficient diet, ad libitum, the other, pair-fed with the same diet, but given supplemental zinc in the drinking water (8 mg Zn++/ml) were studied. After ten weeks of diet, rats were exsanguinated and zinc and calmodulin concentrations in brain and testis were measured. Mean zinc concentration in testis was significantly decreased in rats fed zinc-deficient diet without supplemental Zn++, but mean zinc concentration in brain was not different. Similarly, mean calmodulin concentration in testis was decreased in rats fed zinc-deficient diet without supplemental Zn++ whereas mean calmodulin concentration in brain was not different. Distribution studies of zinc and calmodulin showed that both zinc and calmodulin were released more freely into soluble fractions of testis in rats fed zinc-deficient diet without supplemental Zn++. These results indicate, for the first time in in vivo studies, that zinc influences the calmodulin content of testis.     

Effect of folate deficiency on placental DNA methylation in hyperhomocysteinemic rats

We report that the maternal folate status can influence folate-mediated one-carbon metabolism and DNA methylation in the placenta. Thirty-six female Sprague-Dawley rats were divided into the following three dietary groups: folate-supplemented (FS; 8 mg/kg folic acid, n=12), homocystine- and folate-supplemented (HFS; 0.3% homocystine and 8 mg/kg folic acid, n=12) and homocystine-supplemented and folate-deficient (HFD; 0.3% homocystine and no folic acid, n=12). The animals were fed their experimental diets from 4 weeks prior to mating until Day 20 of pregnancy (n=7-9 per group). The HFS diet increased the plasma homocysteine and placental DNA methylation but did not affect plasma folate, vitamin B-12, S-adenosyl methionine (SAM) or S-adenosyl homocysteine (SAH) levels, or the SAM/SAH ratio in the liver and placenta compared with the FS diet. The HFD diet induced severely low plasma folate concentrations, with plasma homocysteine levels increasing up to 100 micromol/L, and increased hepatic SAH and decreased placental SAM levels and SAM/SAH ratio in both tissues, with a concomitant decrease in placental DNA methylation. Placental DNA methylation was significantly correlated with placental (gamma=0.819), hepatic (gamma=0.7) and plasma (gamma=0.752) folate levels; plasma homocysteine level (gamma=-0.688); hepatic SAH level (gamma=-0.662) and hepatic SAM/SAH ratio (gamma=0.494). These results suggest that the maternal folate status in hyperhomocysteinemic rats influences the homeostasis of folate-mediated one-carbon metabolism and the methyl pool, which would, in turn, affect placental DNA methylation by altering the methylation potential of the liver.     

Tracing of Zinc Nanocrystals in the Anterior Pituitary of Zinc-Deficient Wistar Rats

The aim of this study was to trace zinc nanocrystals in the anterior pituitary of zinc-deficient Wistar rats by using autometallographic technique. Male Wistar rats (30–40 days of age, pre-pubertal period) of 40–50 g body weight were divided into the following: the ZC (zinc control) group—fed with 100 ppm zinc in diet, the ZD (zinc-deficient) group—fed with zinc-deficient (1.00 ppm) diet and the PF (pair-fed) group—received 100 ppm zinc in diet. The experiments were set for 2 and 4 weeks. Pituitary was removed and processed for the autometallographic technique. The control and pair-fed groups retained their normal morphological features. However, male Wistar rats fed on zinc-deficient diet for 2 and 4 weeks displayed a wide range of symptoms such as significant (P < 0.05) decrease in diet consumption, body weight and pituitary weight and decrease in gradation of intensity of zinc nanocrystals in the nuclei. The present findings suggest that the dietary zinc deficiency causes decreased intensity of zinc nanocrystals localization and their distribution in the pituitary thereby contributing to the dysfunction of the pituitary of the male Wistar rats. The severity of zinc deficiency symptoms progressed after the second week of the experiment. Decreased intensity of zinc nanocrystals attenuates the pituitary function which would exert its affect on other endocrine organs impairing their functions indicating that the metabolic regulation of pituitary is mediated to a certain extent by zinc and/or hypothalamus-hypophysial system which also reflects its essentiality during the period of growth.     

Effects of dietary zinc on free radical generation, lipid peroxidation, and superoxide dismutase in trained mice.

The purpose of this study was to investigate the effects of dietary zinc on free radical generation, lipid peroxidation, and superoxide dismutase (SOD) in exercised mice. In the first part of the study, 48 male weanling mice were randomly divided into three groups. They were fed a zinc-deficient diet containing 1.6 mg/kg zinc or were pair-fed or fed ad libitum a zinc-adequate diet supplemented with 50 mg/kg zinc. Half of each group received an exercise training program that consisted of swimming for 60 min per day in deionized water. The diets and exercise program persisted for 6 weeks. In the second part of the study, 64 mice were fed zinc-deficient diets for 6 weeks, and then one group was fed the zinc-deficient diet for an additional 3 weeks, and the other three groups were fed diets supplemented with 5, 50, and 500 mg/kg zinc, respectively. Half of each group also received the exercise program. Both blood and liver samples were examined. Free radicals in liver were directly detected by electron spin resonance techniques and the extent of lipid peroxidation was indicated by malonic dialdehyde (MDA). Both CuZn-SOD and Mn-SOD were measured. The results showed that exercise training increased the metabolism of zinc, and zinc deficiency induced an increased free radical generation and lipid peroxidation and a decreased hepatic CuZn-SOD activity in exercised mice. Furthermore, although exercise training had no effect on the level of free radicals in zinc-adequate mice, it could increase the hepatic mitochondrial MDA formation further in zinc-deficient animals and zinc deficiency would eliminate the exercise-induced increase in SOD activities which existed in zinc-adequate mice. A total of 50 mg/kg zinc supplemented in the diet was adequate to correct the zinc-deficient status in exercised mice while 5 mg/kg zinc had a satisfactory effect on the recovery of only sedentary zinc-deficient mice. However, 500 mg/kg zinc had a harmful effect on both sedentary and exercised zinc-deficient animals.     

The effect of zinc deficiency and food restriction on prostaglandin E2 and thromboxane B2 in saliva and plasma of rats

Zinc has been implicated in the regulation of prostaglandins and other arachidonic acid derivatives. Studies of zinc-deficient animals, however, are compromised by concomitant reduction in food intake that may also alter eicosanoid levels in body tissues and fluids. In this study, three groups of rats, designated as zinc-deficient, pair-fed and control, were fed diets containing 1 ppm, 15 ppm (in amounts paired to deficient rats) and 15 ppm Zn ad libitum, respectively, for 6 weeks. Saliva and blood were analyzed for PGE2 and TXB2 by radioimmunoassay. Saliva concentrations of both eicosanoids were lower (p less than 0.05) in the pair-fed animals, but not significantly altered by zinc deficiency. Plasma levels of PGE2 and TXB2 were unchanged by either zinc deficiency or food restriction. The results of this study support the contention that the effect of zinc on these prostaglandins is not mediated by altered rates of synthesis or degradation but rather by effects on eicosanoid function.     

Differences in the mineral contents between falx cerebri and tentorium cerebelli

A study was performed to determine the effect of zinc deficiency on the zinc concentration of the retina, lens, and the retinal pigment epithelium and choroid. Weanling, male Sprague-Dawley rats were fed ad libitum modified AIN-93 diets containing 3 mg zinc/kg diet (−Zn; n=10) for 6 wk. Control animals were pair-fed (+ZnPF; n=10) or fed ad libitum (+ZnAL; n=10) diets containing 100 mg zinc/kg diet. At 6 wk, plasma and tibia zinc were measured by flame atomic absorption spectrophotometry to confirm zinc deficiency. The zinc concentration of ocular tissues was measured by inductively coupled plasma-mass spectrometry. Mean (±SEM) lens zinc concentration was significantly depressed in the zinc-deficient group as compared to that of pair-fed or ad libitum-fed controls, suggesting that the role of zinc in cataract formation should be investigated. The zinc concentration of total neural retina was preserved in zinc deficiency. Previously reported deterioration of retinal function in zinc deficiency may be the result of a decline in the zinc concentration of a specific cell layer of the retina that cannot be detected on gross analysis of the entire retina. This work was presented in part at Experimental Biology 98, April 1998, San Francisco, CA [P. G. Paterson, B. H. Grahn, and J. S. Fabe, Retinal and lens zinc concentration in the zinc-deficient rat. FASEB J. 12, A521 (1998)].     

Genetic and nutritional deficiencies in folate metabolism influence tumorigenicity in Apcmin/+ mice

Epidemiological studies indicate that adequate dietary folate is protective against colon cancer, although mechanisms remain largely elusive. We investigated the effects of genetic disruptions of folate transport and metabolism and of dietary folate deficiency in a mouse model of colon cancer, the Apc(min/+) mouse. Apc(min/+) mice with heterozygous knockout of the gene for reduced folate carrier 1 (Rfc1(+/-)) developed significantly fewer adenomas compared to Rfc1(+/+)Apc(min/+) mice [30.3+/-4.6 vs. 60.4+/-9.4 on a control diet (CD) and 42.6+/-4.4 vs. 55.8+/-7.6 on a folate-deficient diet, respectively]. Rfc1(+/-)Apc(min/+) mice also carried a lower tumor load, an indicator of tumor size as well as of tumor number. In contrast, there were no differences in adenoma formation between Apc(min/+) mice carrying a knockout allele for methionine synthase (Mtr(+/-)), an enzyme that catalyzes folate-dependent homocysteine remethylation, and Mtr(+/+)Apc(min/+) mice. However, in both Mtr groups of mice, dietary folate deficiency significantly increased adenoma number (from 32.3+/-3.8 on a CD to 48.1+/-4.2 on a folate-deficient diet), increased plasma homocysteine, decreased global DNA methylation in preneoplastic intestines and increased apoptosis in tissues. There were no genotype-associated differences in these parameters in the Rfc1 group, suggesting that the protection conferred by Rfc1 deficiency is carried out through a different mechanism. In conclusion, genetic and nutritional disturbances in folate metabolism can have distinct influences on tumorigenesis in Apc(min/+) mice; altered levels of homocysteine, global DNA methylation and apoptosis may contribute mechanistically to dietary influence.     

Influence of zinc depletion and zinc status on serum growth hormone levels in rats

In a preceding trial, the growth hormone concentrations in the serum of zinc-deficient rats were greatly reduced compared to thead libitum- fed control animals. The same reduction, however, was also noted in the case of the pair-fed control animals with strongly diminished feed intake. Therefore, it was not possible to distinguish between the effects of zinc deficiencyper se and the effects resulting from restricted feed intake. A new study with 136 young male Sprague-Dawley rats showed again that zinc deficiency as well as strongly restricted feed intake reduced the growth hormone content in the serum. But in a marginal zinc deficiency status, when feed intake was only slightly or not reduced, there were lowered serum growth hormone levels in comparison to pair-fed control rats. A 1-wk zinc repletion did not increase the serum growth hormone content of the rats to a normal level, although the serum zinc concentration was normalized.     

Effects of Actinomycin D and Cycloheximide on Zinc Status in Marginally Zinc-Deficient Rats

During deficient zinc intake, rats are liable to suffer zinc deficiency under the following conditions: higher protein diet, diet containing higher quality (higher nutritive value) protein, and higher dietary intake. This suggests that a higher protein nutritional status (rapid increase in body protein) in rats leads to a lower zinc nutritional status (higher zinc requirement). In contrast, it is expected that a lower protein nutritional status (lowered body protein biosynthesis) is not liable to result in a lower zinc nutritional status. Therefore, the effects of protein biosynthesis inhibitors on zinc status were studied. Actinomycin D and cycloheximide were administered to rats under a marginally zinc-deficient condition. The growth of rats was depressed and serum and femur zinc concentrations were increased by administration of protein biosynthesis inhibitors. The carcasses of rats administered protein synthesis inhibitors had a higher zinc/protein ratio than those of the respective pair-fed (calorically equivalent to the zinc-deficient group) rats. Results suggest that zinc deficiency in rats is mainly alleviated by decreased food intake with administration of protein synthesis inhibitors. Furthermore, protein biosynthesis inhibition alone alleviated zinc deficiency.     

Teratogenicity of zinc deficiency in the rat: study of the fetal skeleton

Zinc deficiency (ZD) is teratogenic in rats, and fetal skeletal defects are prominent. This study identifies fetal skeletal malformations that affect calcified and non-calcified bone tissue as a result of gestational zinc deficiency in rats, and it assesses the effect of maternal ZD in fetal bone calcification. Pregnant Sprague-Dawley rats (180-250 g) were fed 1) a control diet (76.4 micrograms Zn/g diet) ad libitum (group C), 2) a zinc-deficient diet (0 microgram/g) ad libitum (group ZD), or 3) the control diet pair-fed to the ZD rats (group PF). On day 21 of gestation, laparotomies were performed. Fetuses were weighed, examined for external malformations, and stained in toto with a double-staining technique for the study of skeletal malformations. Maternal and fetal tissues were used for Zn, Mg, Ca, and P determinations. Gross external malformations were present in 97% of the ZD fetuses. No external malformations were found in fetuses from groups C and PF. Ninety-one percent of cleared ZD fetuses had multiple skeletal malformations, whereas only 3% of the fetuses of group PF had skeletal defects; no skeletal malformations were found in fetuses from group C. Some of the skeletal malformations described in the ZD fetuses, mainly affecting non-calcified bone, were not mentioned in previous reports, thus stressing the importance of using double-staining techniques. Examination of stained fetuses and counting of ossification centers revealed important calcification defects in ZD fetuses. These effects were confirmed by lower Ca and P concentrations in fetal bone with alteration of the Ca:P ratio.     

Both zinc deficiency and supplementation affect plasma melatonin levels in rats

At physiological levels, zinc and various hormones affect each other reciprocally. Reduction in zinc levels in pinealectomized rats suggests the relation between zinc and melatonin. The effect of both zinc deficiency and supplementation on plasma melatonin levels in rats were investigated in this study. The study was done in Sel?uk University, Experimental Medicine Research and Application Center. Twenty-four adult male Sprague Dawley rats were divided into 3 groups. Eight rats were fed with zinc-deficient diet. Zinc supplementation was administered intaperitoneally to 8 rats. The remaining 8 rats were used as controls. All rats sacrificed 3 weeks later. Plasma melatonin and zinc levels were determined. The plasma zinc levels of the zinc-supplemented group were higher than those of the other groups as expected (P<0.01). Similarly, the melatonin levels in the zinc-supplemented group were higher than those in the other groups. A significant decrease was observed in melatonin levels of the zinc-deficient group compared to the control and zinc-supplemented group (P<0.01). The results of this study suggest that zinc deficiency decreases the melatonin levels and zinc supplementation may increase the plasma melatonin levels in rats.     

Hepatic insulin binding following in utero exposure to ethanol

Insulin binding to liver membranes has been studied in term fetuses of rats fed ethanol-containing liquid diet during pregnancy . Pair-fed and ad libitum-fed controls received liquid diet in which maltose-dextrins were substituted isocalorically for ethanol. Food consumption and body weigh gain of ethanol- imbibing dams were 35% and 70% less than their ad libitum counterparts respectively. Ethanol-fed rats also exhibited less gain in body weight than pair-fed controls despite isocalorically equivalent food intake. The number of live pups was not different among the various groups; however, liver weight of fetuses exposed to ethanol in utero was 47% less than those of the pups of ad libitum control dams and 28% less than those of the offspring of pair-fed control rats. Insulin binding to liver membranes of fetuses exposed to ethanol in utero was lower than that of ad libitum controls but was not significantly different from that of the pair-fed control animals. Average affinity profiles showed a reduction in K at all levels of receptor occupancy in the fetuses of ethanol-fed rats. For fetuses of the pair-fed group, K was reduced only at fractional occupancy below 20% but not at higher fractional occupancy. Because of the similarity of insulin binding in the fetuses of the ethanol-fed rats and their pair-fed counterparts, effects of ethanol on insulin binding cannot account for the reduced hepatic glycogen stores previously reported in term fetuses.     

Chronic ethanol feeding inhibits plasma levels of insulin-like growth factor-1

The purpose of this study was to determine whether the generalized catabolic effects of chronic ethanol may be associated with a decline in plasma levels of insulin-like growth factor-1 (IGF-1). Male Sprague-Dawley rats were fed a liquid diet containing 5% ethanol or pair-fed a diet made isocaloric with maltose-dextrin. Animals were maintained on this diet for either 12 days or 4.5 months. Another group of animals were fed control diet ad libitum for 2 weeks. After 12 days of feeding, plasma concentrations of IGF-1 in ad libitum fed rats were 771 +/- 41 ng/ml which was greater than concentrations in either pair-fed (595 +/- 23 ng/ml) or ethanol-fed (680 +/- 40 ng/ml) rats (P less than 0.05). After 4.5 months of feeding, plasma levels of IGF-1 in ad libitum and pair-fed rats were similar to the 12 day study (736 +/- 56 and 607 +/- 26 ng/ml, respectively). However, a significant decrease in plasma levels of IGF-1 was observed in ethanol-fed animals over the 4.5 month period (551 +/- 28 ng/ml, P less than 0.05). Results of a similar study in rats fed a high-fat diet for 4.5 months were similar to those found with the low-fat diet. These results indicate that 1) dietary restriction of the type routinely used in this pair-feeding regimen decreases plasma levels of IGF-1, 2) chronic ethanol feeding further decreases plasma IGF-1 levels compared to pair-fed rats, 3) the effects of ethanol on IGF-1 concentrations are not modified by dietary fat, and 4) the effects on IGF-1 are not directly dependent on elevated plasma ethanol concentrations. Our results suggest that IGF-1 secreting cells in the liver may be progressively damaged by chronic ethanol feeding.