Abstract
BackgroundPreviously, we documented the presence of ovulation-inducing factor (OIF) in the seminal plasma of llamas and alpacas. The purpose of the study was to define the biochemical characteristics of the molecule(s) in seminal plasma responsible for inducing ovulation.MethodsIn Experiment 1, llama seminal plasma was centrifuged using filtration devices with nominal molecular mass cut-offs of 30, 10 and 5 kDa. Female llamas (n = 9 per group) were treated i.m. with whole seminal plasma (positive control), phosphate-buffered saline (negative control), or the fraction of seminal plasma equal or higher than 30 kDa, 10 to 30 kDa, 5 to 10 kDa, or < 5 kDa. In Experiment 2, female llamas (n = 7 per group) were given an i.m. dose of seminal plasma treated previously by: 1) enzymatic digestion with proteinase-K, 2) incubation with charcoal-dextran, 3) heating to 65°C, or 4) untreated (control). In Experiment 3, female llamas (n = 10 per group) were given an i.m. dose of pronase-treated or non-treated (control) seminal plasma. In all experiments, llamas were examined by transrectal ultrasonography to detect ovulation and CL formation. Ovulation rate was compared among groups by Fisher's exact test and follicle and CL diameters were compared among groups by analyses of variance or student's t-tests.ResultsIn Experiment 1, all llamas in the equal or higher than 30 kDa and positive control groups ovulated (9/9 in each), but none ovulated in the other groups (P < 0.001). In Experiment 2, ovulations were detected in all llamas in each treatment group; i.e., respective treatments of seminal plasma failed to inactivate the ovulation-inducing factor. In Experiment 3, ovulations were detected in 0/10 llamas given pronase-treated seminal plasma and in 9/10 controls (P < 0.01).ConclusionsWe conclude that ovulation-inducing factor (OIF) in llama seminal plasma is a protein molecule that is resistant to heat and enzymatic digestion with proteinase K, and has a molecular mass of approximately equal or higher than 30 kDa.
Highlights
We documented the presence of ovulation-inducing factor (OIF) in the seminal plasma of llamas and alpacas
Experiment 1 - molecular mass cut-off The diameter of the largest follicle at the time of treatment did not differ (P = 0.9) among treatment groups and ovulation was observed in only those treated with the ≥ 30 kDa fraction or whole seminal plasma (Table 1)
No ovulations were detected in llamas given lower molecular mass fractions of seminal plasma or in those given PBS
Summary
We documented the presence of ovulation-inducing factor (OIF) in the seminal plasma of llamas and alpacas. The purpose of the study was to define the biochemical characteristics of the molecule(s) in seminal plasma responsible for inducing ovulation. In his monograph of The Biochemistry of Semen nearly 50 years ago, Thaddeus Mann summarized the natural properties of seminal plasma as a vehicle for sperm transport, a controller of sperm motility and capacitation, and as a stimulant of uterine contractility [1]. Based on LH secretion from primary cultures of rat pituitary cells [9], the putative ovulation-inducing factor in alpaca seminal plasma had GnRH-like activity but was not GnRH since its biological activity was not suppressed when antiGnRH antibodies were added to the culture medium
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