Effect of Zinc on Rat Uterine Metabolism

UNCP Author/Contributor (non-UNCP co-authors, if there are any, appear on document)
Jayne Connor (Creator)
The University of North Carolina at Pembroke (UNCP )
Web Site: http://www.uncp.edu/academics/library

Abstract: The discovery by Zipper (1) that a copper or zinc wire on a polyethylene intrauterine device (IUD) enhances the contraceptive effect has stimulated interest in these divalent cations as contraceptive materials. The bulk of subsequent research has centered upon the use of copper rather than zinc. These studies have shown that enhancement of the contraceptive effect apparently requires the release of copper ions and is not due to the physical presence of the IUD (2). A brief review of the biological roles of zinc follows.More than 25 zinc containing proteins, most of which are enzymes, have been identified (3). The integrity and stability of the DNA double helix, ribosomes and biomembranes depend upon zinc (4,5). Plasma zinc concentration decreases to a deficiency range if zinc is removed from the diet. Nonfunctional zinc is tightly bound and cannot be shifted within the body to meet crucial needs (6).At a low concentration (2M), zinc inhibits the electron transport chain in mitochondria. The low respiratory activity of spermatozoa may be due to the high cellular content of zinc. This suggests a specific and effective role of zinc in the control of respiration (4).Many studies have shown that the contraceptive effect is manifested through an action on the endometrium by rendering it hostile to implantation (7). Hagenfeldt (8) has show that a continuous decrease of the zinc concentration in the secretory endometrium occurs when the copper IUD is in situ. This suggests a decrease in the synthesis of zinc containing enzymes, which may contribute to the contraceptive effect. Oster has reported the inhibition of the activities of the zinc enzymes alkaline phosphatase and carbonic anhydrase (9). Other possibilities explaining this contraceptive effect, such as the role of estradiol action and possibly its uptake, have been suggested. Some investigations using rats have indicated a possible alteration of estradiol uptake by uteri exposed to copper IUD's. The results of these experiments are, however, contradictory. Chang and Tatum reported no alteration of uptake (10). Aedo and Zipper found an increase in estradiol uptake by the uterus (11), whereas Ghosh found a decrease in uptake (12).It has been found that in vitro binding of estradiol to uterine receptors is affected by divalent cations. Emanuel and Oakey found an increase of estradiol binding to uterine tissue, zinc providing to be the most effective of those tested (13). Most researchers have found an increase of binding by divalent cations, though Brecher found zinc to decrease estradiol binding (14).Therefore, there is good evidence that zine and copper may affect estradiol binding in the uterus. One of the questions these findings pose is whether this copper and zinc induced binding is of physiological importance. That is, does the increased estradiol binding significantly alter the basal physiological state of the uterus? If estradiol binding is altered and if that alteration is of physiological importance, then a corresponding effect on uterine metabolism is expected. Nicollete and Gorski have show that estrogen causes a two fold increase in the incorporation of 14C from labeled glucose into uterine carbon dioxide, lipid, protein and RNA(15). Maxwell (16) has reported that copper elicits a similar stimulation of uterine glucose metabolism. The primary objective of this project was to monitor the incorporation of glucose derived carbon into these metabolic end points.

Additional Information

Language: English
Date: 1979
Contraceptive, Zinc, Polyethylene Intrauterine Device, IUD, Copper

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