Effect of zinc deficiency on appetite and plasma amino acid concentrations in the rat

Abstract

1. Levels of zinc in liver and plasma of the Zn-depleted rats fluctuated with the feeding cycle and were significantly higher at the bottom than at the top of the cycle. As Zn deficiency became more severe fluctuations in plasma Zn diminished. Concentrations of Zn in liver, in contrast to levels in plasma and femur, were not markedly lowered by day 15. 2.In contrast to udlib.-fed (AL) and overnight-fasted (OF) controls, some pair-fed (PF) controls had elevated levels of Zn in liver and plasma.3. Intakes of water and food were sigdicantly correlated in Zn-deficient rats. Packed cell volumes were significantly higher for Zn-depleted than for AL and PF rats.4. Food intakes and plasma glucose concentrations were related in AL, OF and PF control rats but not in Zndeficient rats. At day 15of Zn deficiency the order of total plasma amino acid concentrations in the groups of rats was AL > Zndeficient > OF > PF. Many of the differences between the AL and OF groups for individual plasma amino acids also appeared in the Zn-deficient group at the top and bottom of the feeding cycle. Differences in individual amino acid conmntrations at the top and bottom of the feeding cycle tended to be opposite in the PF and the Zn-ddicient group. Levels of tyrosine and tryptophan in plasma were correlated (P < 0.05) with the cyclic feeding pattern of the Zn-deficient group; however, the ratios tryptophan or tyrosine: sum of other large neutral amino acids did not correlate significantly with the eating habits of Zndeficient rats.

Analysis of cyclic feed intake in rats fed on a zinc-deficient diet and the level of dihydropyrimidinase (EC3.5.2.2)

“…This reduction in feed intake was previously reported to be accompanied by a pattern of cyclic feeding in rats with Zn-deficient diet (Mills et al 1969;Chesters & Quarterman, 1970;Chesters & Will, 1973;Wallwork et al 1981;Gingliano & Millward, 1984;Kramer et al 1984;Quinn et al 1990). Here, we found by Cosinor analysis that the period of the cycle was 3.5 (SE 0.1) d. These results suggest that rats fed on Zn-deficient diet show little variation in feeding pattern, which consistently shows a cycle of 3.5 d.…”

“…Fig. 2a illustrates the cyclic feeding pattern of five Zn-deficient rats, which has been described by others (Mills et al 1969;Chesters & Quarterman, 1970;Wallwork et al 1981;Kramer et al 1984). The values of the rhythmometric parameters obtained by Cosinor analysis are shown in Table 2.…”

“…If the tissues being lost and gained in a cyclical manner contain, say, 80 % or more water, the differences could largely be explained on this basis. In fact, daily intakes of water and feed are closely correlated for the Zn-deficient rats (Wallwork et al 1981). Therefore, the amplitude in body weight may be about twice that in feed intake.…”

“…Failure of growth during Zn deficiency in vivo is complex, with cyclical changes in feed intake (Mills et al 1969;Chesters & Quarterman, 1970;Chesters & Will, 1973;Wallwork et al 1981;Gingliano & Millward, 1984;Kramer et al 1%4;Quinn et al 1990), body weight (Wallwork et al 1981;Gingliano & Millward, 1984), and muscle mass (Gingliano & Millward, 1984). Zn deficiency impairs growth by a combination of decreased feed intake, lowered anabolic response to the feed, and increased catabolic response (Ginghano & Millward, 1984).…”

The effect of growth hormone treatment on growth in zinc deficient rats

“…deficient animaIs remain nibblers (Chesters and Quarterman, 1970;Wallwork ~~, 1981). This altering of the frequency of food ingestion may result in differences in nutrient metabolism and body composition (Fabry and Braun, 1967;Leveille, 1972).…”