LH release and ovulatory response after intramuscular, intravenous, and intrauterine administration of β-nerve growth factor of seminal plasma origin in female llamas

Abstract

The objective of the study was to compare the pituitary and ovarian responses after intramuscular, intravenous, or intrauterine administration of β-nerve growth factor (β-NGF) of seminal plasma origin (SP-NGF) in llamas. In experiment 1, mature female llamas with a growing follicle of 7 mm or greater were assigned randomly to four groups (n = 7/group) and given 2 mg of purified SP-NGF in a volume of 2 mL by (1) intramuscular administration, (2) intravenous administration, and (3) intrauterine infusion, or (4) intrauterine infusion of 2 mL of PBS (negative control). Because ovulations were not detected after intrauterine infusion in experiment 1, a second experiment was done to determine if a higher dose of SP-NGF given by intrauterine infusion, similar to a natural dose during copulation, will elicit an ovulatory response. In experiment 2, llamas with a growing follicle of 7 mm or greater were assigned randomly to three groups (n = 6/per group) given an intrauterine infusion of (1) 4 mL of raw seminal plasma, (2) 4 mL of PBS containing 20 mg of purified llama SP-NGF, or 3) 4 mL of PBS (negative control). In both experiments, the ovaries were examined daily by transrectal ultrasonography using a B-mode scanner and power Doppler mode to detect ovulation and to monitor CL growth, regression, and vascularization. Blood samples were collected to determine plasma LH and progesterone concentrations. In experiment 1, only llamas treated by intramuscular or intravenous administration of SP-NGF ovulated (7 of 7 and 6 of 7, respectively). Plasma LH concentration did not differ between the intramuscular and intravenous SP-NGF-treated groups, nor did CL diameter, CL vascularization, or plasma progesterone concentration profiles. In experiment 2, the ovulation rate was 100% for llamas treated by intrauterine infusion of raw seminal plasma or llama SP-NFG, whereas no ovulations were detected in females treated with PBS. Plasma LH concentrations did not differ between groups that ovulated, nor did CL diameter, CL vascularization, or plasma progesterone concentration profiles. We conclude that β-NGF from llama seminal plasma origin elicits a preovulatory LH surge, followed by ovulation and the development of a functional CL, regardless of the route of administration. However, the dose required to elicit pituitary and ovarian responses is higher when administered by intrauterine infusion than by intramuscular or intravenous routes.

Keywords: CL development; Induced ovulation; Seminal plasma; llama; β-Nerve growth factor.