Abstract
Canine overpopulation continues to be a problem with serious public health implications, despite a diversity of programs and strategies that have been implemented for its control. Coumestrol (COU) is an organic compound with estrogenic activity, thus having the potential to alter reproduction in mammals. COU is commonly dissolved in dimethyl sulfoxide (DMSO) before administration; however, evidence indicates that DMSO is not inert. The aim of this study was to assess the effects of either a single oral administration of COU diluted in DMSO or of DMSO-alone, on serum progesterone (P4) and estradiol (E2), on vaginal cell pattern, and on anestrus and diestrus lengths in bitches. Fifteen anestrus female dogs received either a single commercial dog food biscuit (Control, n=5), a biscuit with 600 μg of COU/kg diluted in 20 μL of DMSO (COU, n=5), or a biscuit with 20 μL of DMSO (DMSO, n=5). Circulating P4, E2, and changes in vaginal cytology, were assessed within the first month after treatment administration. Hormone levels were also measured from months 2-6 post-treatment. Mean differences were analyzed by the GLM procedure for repeated measures. COU enhanced serum E2 levels, and DMSO increased serum P4, number of vaginal anucleated superficial cells, and diestrus length. All dogs were deemed healthy based on all periodical clinical exams, but abnormal mammary gland growth and/or galactorrhea were observed in two COU and one DMSO-treated bitches. The findings of the present study expose the need to reevaluate previous reports of use of COU in bitches, and perhaps in other mammals.Figure 1. Progesterone (A) and estradiol (B) serum levels in anoestrous bitches receiving a commercial dog food biscuit alone (Control; n=5), a biscuit with coumestrol diluted in dimethyl sulfoxide (COU; n=5), or a biscuit with only dimethyl sulfoxide (DMSO; n=5). a,b Different letters within sampling day indicate difference between treatments (P<0.05).*specifies statistical increase on post-treatment days 21 (P<0.0048) and 28 (0.0008). Data are presented as LSM ± standard error.
Highlights
Dogs have had a close and positive relationship with humans for approximately 15,000 years.[1,2] worldwide canine overpopulation has increasingly turned into a serious public health problem, in underdeveloped countries.[3,4]Several programs and strategies have been implemented to control this problem
During early and mid-anestrus, the hypothalamus and ovaries of bitches are relatively inactive. This condition changes during late anestrus, when there is an increase in expression of genes encoding for estrogen receptors, and for the P450 aromatase enzyme, which enhance estrogen biosynthesis in preparation for a new estrous cycle.[7]
Our findings show for the first time that dimethyl sulfoxide (DMSO) by itself has estrogenic effects in anestrus bitches
Summary
Several programs and strategies have been implemented to control this problem. These have mostly been insufficient or unsuccessful, due to attached economic, ethical and/or social constraints.[5,6] there is a need to continue searching for adequate alternatives to control canine reproduction. During early and mid-anestrus, the hypothalamus and ovaries of bitches are relatively inactive. This condition changes during late anestrus, when there is an increase in expression of genes encoding for estrogen receptors, and for the P450 aromatase enzyme, which enhance estrogen biosynthesis in preparation for a new estrous cycle.[7] Both estradiol (E2) and progesterone (P4) have fundamental roles in periodicity of the estrous cycles in bitches.[8]
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