| Abstrakt: |
Adult female rats were given a low zinc diet (<1 ppm) for 8–9 weeks after which some of the females were repleted with zinc on either a restricted food intake or an ad lib. intake. Repletion times were 10 days in experiment 1, 25 and 32 days in experiment 2, and 25 days in experiment 3. At the end of each experiment blood was collected by heart puncture, and pituitary and hypothalamic tissue was removed. Luteinizing hormone-releasing factor (LRF) was measured by injecting pooled hypothalamic extracts into the carotid arteries of male rats and measuring luteinizing hormone (LH) in blood collected 5 min later. LH was measured by radioimmunoassay of blood plasma from males and females and on pooled pituitaries from females. Plasma LH in the zinc-deficient and restricted-intake females was generally lower than in the controls. Plasma progesterone (measured in experiment 3 only) was significantly lower in the deficient and restricted-intake groups than in the controls. The low plasma LH in the zinc-deficient and restricted-intake females did not appear to be due to a lack of LRF, however, since LRF was generally as high in these females as in the controls. Values for LH and LRF in the zinc-deficient females were never higher than those in the controls, whereas in the restricted-intake females there were instances in which values for LH (experiment 2, 25-day repletion) and LRF (experiment 2, 32-day repletion) were significantly increased compared to the controls. Since the females that were subjected only to food restriction were at times able to increase their production of LH or LRF, whereas the zinc-deficient females were not, zinc deficiency appears to have an effect on reproduction in addition to its effect on food intake. |
