A cellular and endocrine characterization of the original and induced corpus luteum after administration of a gonadotropin-releasing hormone agonist or human chorionic gonadotropin on day five of the estrous cycle

• Published in: Journal of animal science Vol. 74; no. 8; p. 1915
• Main Authors: Schmitt, E.J.P. (University of Florida, Gainesville.), Barros, C.M, Fields, P.A, Fields, M.J, Diaz, T, Kluge, J.M, Thatcher, W.W
• Format: Journal Article
• Language: English
• Published: United States 01.08.1996
• Subjects: AGONISTAS; AGONISTE; Animals; Buserelin - pharmacology; Cattle - metabolism; Cattle - physiology; CELLULE; CELULAS; Chorionic Gonadotropin - pharmacology; CICLO ESTRAL; CORPS JAUNE; Corpus Luteum - cytology; Corpus Luteum - metabolism; Corpus Luteum - physiology; CUERPO LUTEO; CULTIVO DE TEJIDOS; CULTURE DE TISSU; CYCLE OESTRAL; Dose-Response Relationship, Drug; ESTRUCTURA CELULAR; Estrus - physiology; Female; FONCTION PHYSIOLOGIQUE; FUNCION FISIOLOGICA; GONADOLIBERINE; GONADOTROPHINE; Gonadotropin-Releasing Hormone - agonists; GONADOTROPINAS; HORMONA LIBERADORA DE GONADOTROPINA; HORMONAS; HORMONE; Humans; Luteinizing Hormone - pharmacology; MEDIO DE CULTIVO; Microscopy, Electron - veterinary; MILIEU DE CULTURE; Organ Size; PLASMA SANGUIN; PLASMA SANGUINEO; PROGESTERONA; PROGESTERONE; Progesterone - blood; Progesterone - metabolism; Random Allocation; SECRECION; SECRETION; STRUCTURE CELLULAIRE; Time Factors; ULTRAESTRUCTURA; ULTRASTRUCTURE; VACAS LECHERAS; VACHE LAITIERE
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/1996.7481915x

To determine whether injection of hCG or GnRH-agonist on d 5 after estrus (d 0) has a differential functional effect on an induced and the original corpus luteum (CL), two experiments were conducted. In Exp. 1, nonlactating Holstein cows were injected on d 5 with saline (n = 4; T1), a GnRH-agonist (Buserelin, 8 microgram i.m.; n = 4; T2), or hCG (1,000 IU, i.v., and 2,000 IU, i.m.; n = 4; T3). Induced CL were removed on d 13 and weights were different (GnRH-agonist hCG). In vitro production of progesterone by CL tissue (microgram/g; microgram/CL) was affected by treatment (GnRH-agonist hCG) and dose of LH (ng/mL) in culture media. Experiment 2 was a replicate of Exp. 1, except that the original CL was removed on d 17 for in vitro culture. Day-17 CL weights and in vitro production of progesterone by original CL were not affected by treatment. The daily rate of increase of plasma progesterone from d 6 to d 13 differed: saline GnRH-agonist hCG (P 0.01). From d 14 to 17, the rate of plasma progesterone decrease was not different between treatments. Electron micrographic study of the original and induced CL indicates that LH-like exposure delays involution of steroidogenic luteal cells. In summary, the higher levels of progesterone from d 6 to d 13 of the estrous cycle following an injection of hCG vs GnRH-agonist on d 5 is due to a greater response of hCG-induced CL