Chronic feeding of a low boron diet adversely affects reproduction and development in Xenopus laevis

The aims of this work were as follows: 1) to determine whether a purified d iet currently used for studies with rats was acceptable for reproductive st udies in frogs; and 2) to determine whether frogs are sensitive to a defici t of boron (B) in the diet. Adult Xenopus laevis were fed a nonpurified bee f liver and lung (BLL) diet (310 mu g B/kg), a purified diet supplemented w ith boron (+B; 1850 mu g B/kg), or a purified diet low in boron (-B; 45 mu g B/kg) for 120 d. Frogs fed the BLL and +B diets produced 11.3 and 12.2% n ecrotic eggs, respectively. Abnormal gastrulation occurred in <4% of the fe rtilized eggs in both groups, and 96-h larval survival exceeded 75% in both groups. In contrast, frogs fed the -B diet for 120 d produced a high propo rtion of necrotic eggs (54%). Fertilized embryos from the -B diet-fed frogs showed a high frequency of abnormal gastrulation (26.8%), and >80% of the embryos died before 96 h of development. Mean embryo cell counts at X. laev is developmental stage 7.5 (mid-blastula) were significantly lower in the - B embryos than in the BLL or +B embryos. BLL and -B embryos grown in low bo ron culture media had a high frequency of malformations compared with embry os grown in boron-supplemented media. These studies show that a purified di et that has been used in rodent studies was acceptable for reproduction stu dies in X. laevis. This work also demonstrates that a diet low in boron mar kedly impairs normal reproductive function in adult X. laevis, and that adm inistration of the low boron diet results in an increase in both incidence and severity of adverse effects. In addition, these studies demonstrate the usefulness of the X. laevis model in nutrition studies.