Calcium chloride diluted in ethanol 95% as female sterilizing agent: effect of transcutaneous delivery in rats

Different fertility control methods are investigated as a tool for population control of free-roaming animals. Chemical castration using calcium chloride has been widely studied over the years in males, but there are few studies related to its use in females. Therefore, we aimed to evaluate the local effects, as a potential chemosterilant, of two concentrations of calcium chloride diluted in 95% ethanol when administered by transcutaneous ultrasound-guided intraovarian injection in rats. In this study, 30 female Wistar rats were randomly divided into three treatment groups, which consisted of transcutaneous ultrasound-guided intraovarian injection of: 0.9% sodium chloride solution (GC); 10% calcium chloride diluted in 95% ethanol (G10); 20% calcium chloride diluted in 95% ethanol (G20). The animals were subdivided into two evaluation times, 15 days (n = 5 of each group) and 30 days (n = 5 of each group) after the intraovarian injection. The ovarian diameter was measured using ultrasound image prior and immediately after the injection and after the treatment period. Furthermore, animals' clinical evaluation, estrous cycles assessment, macroscopic examination of the abdominal cavity and histological evaluation of the ovaries were performed.

Ovarian ultrasound measurement revealed changes (p < 0.05) between ovarian diameters before and immediately after the injection in all treatments. Three animals in G20 had a small focal skin lesion at the injection site that evolved to total healing. Extended and abnormal estrous cycles were observed in G10 and G20. At gross examination, adhesions and ovarian cysts were noticed in both groups, G10 and G20. Also, the histopathology analysis revealed changes in ovarian architecture and vessel congestion in G10 and G20, but ovarian tissue damage was greater in the ovaries treated with the highest concentration (G20).

The results indicate that 20% calcium chloride diluted in 95% ethanol may be a potential agent for inducing sterilization in females and was possible to be minimally invasively delivered.