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Dietary boron and erythritol affect reproduction and fetal development in rats. (Professional Communications).

Previous research indicates that physiologic amounts of dietary boron (B) affect reproductive function and embryonic development in frogs (1), fish (2), and mice (3). For example, frog and fish embryos, in the early stages of development, exhibited increased necrosis and delayed growth when parents were fed a low boron diet. The objective of this experiment was to characterize the role of dietary boron in reproduction and development in rats.

In a 2 x 2 factorially-arranged experiment, weanling Sprague-Dawley female rats (13/treatment) were fed a boron-low basal diet (~0.1 mg B/kg) supplemented with boron (as orthoboric acid) at 0 (OB) and 2 (2B) mg/kg, and I-erythritol (E), a boron-binding biomolecule, at 0 (0E) or 5 (5E) mg/kg diet for a erythritol:boron molar ratio of 4 in the OB/5E group. Dietary treatment was maintained for eight weeks prior to and during gestation. The females were bred with similarly fed males (5/treatment), for a 48 hour maximum mating time per individual breeding pair. On gestation day 19, fetuses were dissected from the uterus, weighed, eviscerated, and then fixed in formalin; subsequently all fetuses were skinned, cleared with glycerol, and stained with Alcian blue and Alizarin red for visualization of skeletons (4). Al! fetuses were examined for gross morphological and skeletal defects. The cervical, thoracic, lumbar, and sacral vertebrae were scored for degree of ossification and morphological defects.

The overall pregnancy rate was rather low (45%) but highest in the 2B/0E group (62%) and lowest in the 2B/0E group (31%). Physiologic amounts of boron decreased the number of dams with fetal resorptions (FR) in the absence of erythritol (See Table 1), however, boron increased these numbers in the presence of erythritol (p <0.005). The average number of implantation sites tended to be higher in the boron adequate group (data not shown). Dietary erythritol affected rib development as evidenced by increased incidence of discontinuous rib XI of pups from dams fed supplemental erythritol. Fetal thoracic vertebral morphologic maturation in litters fed physiologic amounts of boron was similar to that observed in commercial chow (~12 mg B/kg) fed rats (in a parallel study). However, vertebral maturation (p <0.02) was accelerated in fetuses from dams fed low amounts of boron as indicated by fewer dumbbell-shaped vertebrae, an earlier stage of vertebral development. Neither boron nor erythritol affected fetal body weight.

Because interrupted ossification of rib XI is typically considered a developmental defect (5), the influence of erythritol on normal skeletal development should be examined further. The findings also suggest a reproductive role for boron that is sometimes influenced by dietary erythritol. Further research is needed to determine whether or not accelerated rates of vertebral ossification during boron deprivation have deleterious consequences on postnatal vertebral structure and function.
Table 1. Effects of Dietary Boron, Erythritol, and Their Interaction
on Reproduction and Fetal Skeletal Development

Dietary Treatment Number Fetal Resorptions
 (mg/kg Diet) of dams (% of dams with at
 B E (n) least one resorption)

 0 0 5 60.0 (0.20-0.90) *
 2 0 8 37.5 (0.13-0.72)
 0 5 6 16.7 (0.02-0.63)
 2 5 4 100.0 (1.00-1.00)

 Logistic Regression Analysis--P Values

Boron NS
Erythritol NS
Boron x Erythritol 0.005

Dietary Treatment Discontinuous Rib XI Dumbbell-Shaped Vertebra
 (mg/kg Diet) (Probability of a (Probability of a
 B E Positive Response) Positive Response)

 0 0 0.171 (0.10-0.28) 0.062 (0.02-{}.!6)
 2 0 0.183 (0.07-0.41) 0.190 (0.09-0.37)
 0 5 0.349 (0.25-0.46) 0.044 (0.024}. i 0)
 2 5 0.368 (0.24-0.52) 0.141 (0.08-0.25)

 Logistic Regression Analysis--P Values

Boron NS 0.020
Erythritol 0.020 NS
Boron x Erythritol -- --

* Numbers in parenthesis reflect logistic regression analysis
confidence intervals.


(1.) Fort, D.J., et al. (1999) J. Nutr., 129, pp 2055-2060.

(2.) Rowe, R.I. and C.D. Eckhert (1999) J. Exp. Biol., 202, pp 1649-1654.

(3.) Lanoue, L., et al. (1998) Biol Trace Elem. Res., 66, pp 271-298.

(4.) Newman, S.M., et al. (1983) Trans. Am. Microsc. Soc., 102, pp 300-305.

(5.) Wise, L.D., et al. (1997) Teratology, 55, pp 249-292.

Kay A. Keehr * and Curtiss D. Hunt USDA, ARS, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202-9034
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Author:Keehr, Kay A.; Hunt, Curtiss D.
Publication:Proceedings of the North Dakota Academy of Science
Article Type:Brief Article
Geographic Code:1U4ND
Date:Apr 1, 2000
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