Ann Pediatr Endocrinol Metab.  2015 Mar;20(1):53-58. 10.6065/apem.2015.20.1.53.

Comparison of growth and pubertal progression in wild type female rats with different bedding types

• Kang BH
• Kim SH
• Jung KA
• Kim SY
• Chung SH
• Park YS
• Yoon KL
• Shim KS

• KMID: 1789532
• DOI: http://doi.org/10.6065/apem.2015.20.1.53

Abstract

PURPOSE
Endocrine-disrupting chemicals interfere with the endocrine system and therefore affect growth and pubertal progression. The study aim was to compare the growth and pubertal progression in wild-type female rats with different bedding types.
METHODS
Twenty 5-week-old female wild-type Sprague Dawley rats were randomly assigned to two groups with different bedding types: one group received wood shaving bedding, while a second group received corncob bedding. We determined crown-rump length and body weight as anthropometric measurements and assessed the serum growth hormone (GH) and estradiol levels. The gh1 mRNA expression levels were compared using quantitative real time transcription polymerase chain reaction. The estrous cycle was evaluated by vaginal smear.
RESULTS
The anthropometric measurements were not significantly different between the two groups. The mean relative expression of the gh1 gene was lower in the corncob bedding group than that in the wood shaving group (P=0.768). Meanwhile serum GH and estradiol were increased in the wood shaving bedding group; however this difference was not statistically significant. The time to first estrus and the length of the estrous cycle were increased in the corncob bedding group; the proportion of normal estrous cycles was also decreased. These findings indicate irregularities in the estrous cycle.
CONCLUSION
Endocrine-disrupting chemicals in corncob bedding might be associated with time to first estrus and length of the estrous cycle. Therefore, the type of bedding should be considered as a factor affecting pubertal progression in rodents.

Keyword

Endocrine disrupting chemicals; Bedding; Growth; Puberty

MeSH Terms

Adolescent
Animals
Bedding and Linens
Body Weight
Crown-Rump Length
Endocrine Disruptors
Endocrine System
Estradiol
Estrous Cycle
Estrus
Female
Growth Hormone
Humans
Polymerase Chain Reaction
Puberty
Rats*
Rats, Sprague-Dawley
RNA, Messenger
Rodentia
Vaginal Smears
Wood
Endocrine Disruptors
Estradiol
Growth Hormone
RNA, Messenger

Figure

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  Fig. 1 Comparison of crown-rump length (A) and body weight (B) between the two groups did not show any significant differences.

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  Fig. 2 Relative expression levels of gh1 gene in wood shaving and corncob bedding were measured by using real-time polymerase chain reaction. Expression of gh1 in the corncob bedding group was reduced by 0.914 times compared to the wood shaving group.

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  Fig. 3 Time to first estrus in each bedding type. The time was significantly delayed in corncob bedding group (P=0.0249).*P<0.05.

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  Fig. 4 Proportion of normal estrus cycles over 3 weeks. The proportion was significantly decreased in corncob bedding group (P=0.0024).*P<0.05.

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  Fig. 5 Estrous cycle length of each bedding type during 3 weeks. The cycle was significantly increased in corncob bedding group (P=0.0062).*P<0.05.

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  Fig. 6 The mean number of normal estrous cycles (proestrus, estrus, metestrus, diestrus) over 3 weeks. The mean numbers of proestrus and estrus phases were decreased (P=0.008 and P=0.042), and that of diestrus was increased in corncob bedding group significantly (P=0.035).

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