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Using vaginal wall impedance to determine estrous cycle phase in Lewis rats

Lab Animal volume 41, pages 122–128 (2012)Cite this article

Abstract

The use of Lewis rats in embryonic tissue transplantation experiments can present a challenge because of the fertility problems associated with this strain. The authors used estrous cycle phase determination to time pairings of reproductively active females and males in order to increase the likelihood that mating would occur. During a 24-month period, female rats in a production colony were evaluated for estrous phase by microscopic evaluation of vaginal smears and by vaginal impedance readings. Pairings that were arranged with females determined to be in the proestrous phase by vaginal smears resulted in a low rate of confirmed matings (14%). Serial vaginal smear sampling also produced a high incidence of pseudopregnancy. Pairings that were arranged with females determined to be in the proestrous phase by vaginal impedance readings resulted in a high rate of confirmed matings (48.1%) as well as a high rate of pregnancy (29.4%). An average of 7.2 embryos were produced per pregnancy. The vaginal impedance technique can be used to improve the breeding success rate of Lewis rats in order to maintain a stable production of embryos for experimentation.

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Figure 1: Procedure for measuring vaginal wall impedance in Lewis rats.
Figure 2: Photomicrographs of dried vaginal smears stained with Wright stain from a female Lewis rat (#21) at different phases of the estrous cycle.
Figure 3: Photomicrographs of dried vaginal smears from female Lewis rats taken after pairing to confirm mating.

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Acknowledgements

We thank Dr. Maria Helena Ortíz and Dr. Gabriela Méndez at the Universidad Católica at Santiago de Chile for their guidance with respect to the reproductive characteristics of the strain; Mrs. Olga Lucía Beltran for her management of the colony; and Dr. Ann Gregory for her review of the manuscript. This study is part of a research project funded by Colciencias and Universidad Javeriana Academic Vice-rectory.

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Authors and Affiliations

  1. Dental Research Center, School of Dentistry, Pontificia Universidad Javeriana, Bogotá, Colombia

    Lorenza María Jaramillo &  Camilo Duran

  2. Institute of Human Genetics, Pontificia Universidad Javeriana School of Medicine, Bogotá, Colombia

    Ignacio Briceño Balcazar

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  1. Lorenza María Jaramillo
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  2. Ignacio Briceño Balcazar
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  3. Camilo Duran
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Correspondence to Camilo Duran.

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Jaramillo, L., Balcazar, I. & Duran, C. Using vaginal wall impedance to determine estrous cycle phase in Lewis rats. Lab Anim 41, 122–128 (2012). https://doi.org/10.1038/laban0512-122

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