Effect of chronic treatment with the gonadotrophin-releasing hormone agonist azagly-nafarelin on basal concentrations of LH in prepubertal bulls

Jimenez-Severiano, H, D'Occhio, MJ, Lunstra, DD, Mussard, ML, Koch, JW, Ehnis, LR, Enright, WJ and Kinder, JE (2003) Effect of chronic treatment with the gonadotrophin-releasing hormone agonist azagly-nafarelin on basal concentrations of LH in prepubertal bulls. Reproduction, 125 2: 225-232. doi:10.1530/rep.0.1250225


Author Jimenez-Severiano, H
D'Occhio, MJ
Lunstra, DD
Mussard, ML
Koch, JW
Ehnis, LR
Enright, WJ
Kinder, JE
Title Effect of chronic treatment with the gonadotrophin-releasing hormone agonist azagly-nafarelin on basal concentrations of LH in prepubertal bulls
Journal name Reproduction   Check publisher's open access policy
ISSN 1470-1626
Publication date 2003
Sub-type Article (original research)
DOI 10.1530/rep.0.1250225
Open Access Status
Volume 125
Issue 2
Start page 225
End page 232
Total pages 8
Place of publication Cambridge
Publisher Soc Reproduction Fertility
Language eng
Abstract Administration of GnRH agonist for an extended period inhibits pulsatile LH release but enhances testicular function of bulls. The mechanism whereby long-term administration of GnRH agonist enhances testosterone concentration in the blood of bulls has not been determined. The aim of this study was to determine whether chronic treatment with the GnRH agonist, azagly-nafarelin, increases blood concentrations of LH and FSH in prepubertal bulls. Two different doses of the GnRH agonist were administered via Alzet mini-osmotic pumps for 28 days. Blood samples were collected at 20 min intervals for 24 h at days 2, 13 and 25 of treatment. Agonist-treated groups had reduced testosterone pulse frequency (P < 0.05) and increased mean and basal concentrations of testosterone (P < 0.05) compared with untreated control bulls. Basal LH concentrations were higher in agonist-treated bulls during all three periods (P < 0.05) and overall 0 ng ml(-1) higher, compared with control bulls; (P < 0.001). Frequency of LH pulses in the agonist-treated groups was reduced to less than one pulse in 24 h. Agonist-treated bulls tended to have (P < 0.10) or had (P < 0.05) a slight but significant increase in blood FSH concentration. In conclusion, the higher blood testosterone concentration in bulls after prolonged treatment with GnRH agonist may result, at least in part, from changes in the testes induced by enhanced basal concentration of LH.
Keyword Developmental Biology
Reproductive Biology
Immature Hypophysectomized Rats
Follicle-stimulating-hormone
Luteinizing-hormone
Leydig-cells
Testosterone Secretion
Plasma-concentrations
Steroidogenic Enzymes
Constant Infusion
Rhesus-monkeys
Young Bulls
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Agriculture and Food Sciences
 
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Created: Fri, 25 Jan 2008, 15:53:25 EST