Superovulatory treatments do not alter pulsatile LH secretion in ovariectomized cattle

• Published in: Theriogenology Vol. 43; no. 3; pp. 543 - 549
• Main Author: Price, C.A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.1995
• Subjects: eCG; FEMELLE; FSH; GONADOLIBERINE; GONADOTROPHINE; GONADOTROPINAS; HEMBRA; HFS; HORMONA LIBERADORA DE GONADOTROPINA; HORMONAS; HORMONE; LH pulses; OVARIECTOMIA; OVARIECTOMIE; SECRECION; SECRETION; SERUM SANGUIN; SUERO SANGUINEO; SUPEROVULACION; SUPEROVULATION; VACAS LECHERAS; VACHE LAITIERE; eCG; LH pulses; FSH; superovulation
• ISSN: 0093-691X; 1879-3231
• DOI: 10.1016/0093-691X(94)00059-4

Previous work has shown a suppressive effect of superovulatory treatments on pulsatile LH release in cattle. This study tested the hypothesis that this suppression may be caused, at least in part, by a direct effect of commercial gonadotropin preparations on the hypothalamus/pituitary gland. Crossbred Holstein heifers, ovariectomized 20 d before the start of the experiment, received 6 injections of FSH (50 mg Folltropin) at 12-h intervals (n = 6); a single injection of 2500 IU eCG followed by 5 injections of sterile saline at 12-h intervals (n = 6); or 6 injections of saline at 12-h intervals (controls; n = 5). Blood samples were taken every 10 min for 8 h the day before and 3 d after the beginning of treatment to assess LH pulsatility. At the end of these sampling periods, a bolus injection of GnRH (7ng/kg) was given to assess pituitary responsiveness. There were no effects of the superovulatory drugs on mean LH concentrations, nor on LH pulse frequency or amplitude (P > 0.05). The pituitary response to GnRH was significantly elevated in eCG- but not FSH-treated animals (paired t test; P < 0.05). These data demonstrate that superovulatory preparations do not suppress pulsatile LH secretion independently of the ovaries in cattle.