Effect of Zinc Nutriture and Contraceptive Steroid Injection on Body Composition of Young Female Rats

Forty-nine female rats initially weighing about 95 grams were used in this experiment to determine the effect of contraceptive hormones on body composition in zinc deficient and zinc supplemented rats. Four treatment groups were: 2 ppm of dietary zinc with daily contraceptive steroid injections, or with placebo injection, and 140 ppm of dietary zinc with contraceptive steroid injection or with placebo. The daily injected steroids consisted of 0.lug of Ethynyl Estradiol and 0.lmg of Medroxyprogesterone in 0.lml of corn oil. Non-hormone treated groups received O.lml of plain corn oil. All injections were administered into the Gluteus Maximus muscle. Food intake, weight gain and serum zinc level were determined weekly. After eight weeks of experimental treatment, animals were killed by decapitation. Livers, adrenals and ovaries were removed, weighed and frozen until cholesterol determinations could be made. The remaining carcass minus the intestinal tract was autoclaved and homogenized. Carcass moisture, ash, total lipid and cholesterol ester levels were determined. Carcass zinc and calcium levels were also determined. The results indicate that zinc deficiency causes a marked loss of appetite with a reduced growth rate and a reduced feed efficiency in the growing female rats. Serum zinc level was also reduced. Rats fed the zinc deficient diet had smaller ovaries than the controls, but their adrenal weights were unaffected. Total cholesterol content of the adrenals was, however, increased. Zinc deficient diet caused a significant elevation of carcass cholesterol esters and carcass water content, and tended to decrease liver cholesterol level. Carcass ash concentration was increased in zinc deficient rats on the basis of fat free samples. Hormone injection caused a slight reduction in growth rate, irrespective of zinc intake, although it slightly improved appetite in the zinc deficient rats, and which caused a slight further decrease in serum zinc level. The relative weight of adrenals and ovaries were significantly decreased by hormone administration, having markedly increased total cholesterol levels. Hormone treatment tended to increase carcass cholesterol ester and liver cholesterol levels. In zinc supplemented rats, carcass total lipids was reduced, while carcass lipid was elevated in zinc deficient rats by hormone injection. Hormone treatment elevated carcass ash content with an increase in its calcium and zinc content which was statistically significant. This increase indicates the anabolic effect of contraceptive steroids on mineral in general