Luteinizing hormone and testosterone concentrations in plasma of bull calves treated with gonadotropin releasing hormone.
Twelve bull calves, 2 to 24 days of age, were assigned to two groups of six calves and administered a single 50 microng intramuscular injection of gonadotropin releasing hormone. Bull calves in group 1 were 2 to 5 days of age (mean 3.0 days), and bull calves in group 2 were 10 to 24 days of age (mean 17.1 days). Blood plasma for radioimmunoassay of luteinizing hormone and testosterone was collected at .5-h intervals for 3-h and at 4- and 6-h following treatment. With increasing age, preinjection luteinizing hormone concentrations in plasma decreased while preinjection testosterone concentrations increased. Mean preinjection luteinizing hormone concentrations for group 1 (1.01 +/- .07 ng/ml; mean +/- standard error) were higher than for group 2 (.61 +/- .12 ng/ml). Preinjection luteinizing hormone and testosterone concentrations were correlated--.63. Following treatment, luteinizing hormone increased with mean peak concentrations of 7.28 +/- .74 and 6.95 +/- 1.79 ng/ml for groups 1 and 2. Peak testosterone response following gonadotropin releasing hormone was higher for group 2 than 1 (1077 +/- 253 versus 436 +/- 116 pg/ml).
D000818:Animals; D000831:Animals, Newborn; D002417:Cattle; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D011863:Radioimmunoassay; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
D010906:Pituitary Hormone-Releasing Hormones; D013739:Testosterone; D007986:Luteinizing Hormone