Submitted to: American Society of Animal Science Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2010
Publication Date: 6/24/2010
Citation: Heidorn, R.S., Barb, C.R., Rogers, C.J., Hausman, G.J., Lents, C.A. 2010. Effects of RFamide-related peptide-3(RFRP-3) on secretion of LH in ovariectomized prepubertal gilts [abstract]. American Society of Animal Science Annual Meeting. Journal of Animal Science. V:88E(Suppl.2) p.566 Interpretive Summary: none
Technical Abstract: Pulses of LH are suppressed prior to puberty in the gilt. RFRP-3 is proposed to be a hypophysiotropic hormone in mammals. A series of experiments (EXP) were conducted to test the hypothesis that RFRP-3 inhibits LH release in ovariectomized (OVX) prepubertal gilts. All gilts were OVX at least two weeks prior to being fitted with indwelling jugular catheters for the collection of serial blood samples. In EXP I, blood samples were collected every 15 min for 6 h. Commencing at 120 min after the start of sampling, all gilts (n = 3) received a loading dose of 1 mg of RFRP-3 followed by repeated injections of 40 µg of RFRP-3 every 5 min for 2 h resulting in a total infusion of 2 mg of RFRP-3. All injections were administered by hand in 2 mL of 0.9% saline. Area under the curve (AUC) was determined in each of 3 periods; 1 h before treatment (period 1), the first h of treatment (period 2), and the second h of treatment (period 3). In EXP II, blood samples were collected every 15 min for 8 h. Commencing at 240 min after the start of sampling, animals received intracerebroventricular (i.c.v) injections of 10, 50, or 100 µg of RFRP-3 in 0.9% saline (n = 6/group). Control animals received 0.9% saline alone (n = 7). AUC was determined for each of two periods (4 h before and 4 h after i.c.v. treatment). Mean LH (1.33 ± 0.13 ng/mL), number of LH pulses (2.0), or pulse amplitude (1.32 ± 0.25 ng/mL) was not different during the 2-h treatment period when compared with 2 h pre- or the 2 h post-treatment. However, there was a tendency (P = 0.09) for total LH release, as indicated by AUC, to be reduced in period 3 compared with periods 1 or 2. In Exp II, Central administration of 10 µg of RFRP-3 yielded an apparent suppression in area under the curve (59.4 ± 20.91% of the pre-i.c.v. value), but this did not reach significance (P = 0.27). We conclude that RFRP-3 does not act to inhibit the pulsatile release of LH in prepubertal gilts.