Evaluation of the effect of mating, intrauterine deposition of raw seminal plasma or seminal plasma purified β-NGF on endometrial vascularization in llamas

Abstract

The aim of this study was to evaluate the endometrial vascularization area (EVA) of both uterine horns in llamas subjected to different intrauterine treatments resembling physiological conditions after a single mating. Llamas with a growing follicle (≥8 mm) were randomly assigned to: a) single mating with a fertile male (mating; positive control; n = 6); b) intramuscular administration of 50 μg of gonadorelin acetate plus an intrauterine infusion of 4 ml of PBS (GnRH; negative control; n = 4); c) intrauterine infusion of 4 ml of raw llama seminal plasma (SP; n = 4) or d) intrauterine infusion of 10 mg of β-NGF purified from llama semen diluted in 4 ml of PBS (spβ-NGF; n = 6). Females in GnRH, SP and NGF group received 50% of treatment volume into each horn by guiding an insemination pipet through the cervix. Ovaries were examined by ultrasonography every 12 h until Day2 (Day 0 = Day of treatment) to determine ovulation. Power-Doppler ultrasonography evaluation of EVA in a cross-section of the middle segment of each horn was conducted at 1 h before and 1, 3, 6, 12 and 24 h (intensive evaluation) and 2, 4, 6 and 8 days (long-term evaluation) after treatment administration. Serial EVA data was analyzed as a 2-by-2 factorial design for repeated measures using the MIXED procedure. The analysis included main effects of treatment (mating, SP, spβ-NGF or GnRH), uterine horn (left vs right), time, and their interactions. According to the 2 by 2 analysis there was no effect of uterine horn on EVA during the first 24 h and from Day 2 to Day 8 after treatment; therefore, data were grouped based on treatment type regardless of uterine horn for both periods of observation. Thus, EVA was affected by time (P < 0.04) and treatment by time interaction (P < 0.02) and tended (P = 0.07) to be influenced by type of treatment during the intensive evaluation period. Females on mating and spβ-NGF group showed a significant increase in EVA at 3 and 12 h after treatment compared to GnRH and SP groups. However, no effect of treatment, time or their interaction was observed during the long-term evaluation period. In spite of the limited number of animals used in this study, our results allow us to concluded that natural mating and intrauterine deposition of 10 mg of spβ-NGF induce a symmetrical increase in endometrial vascularization of both uterine horns during the first 24 h post treatment administration in llamas; however, this effect did not persist beyond that period.