title: Plasma insulin-like peptide 3 concentrations are acutely regulated by luteinizing hormone in pubertal Japanese Black beef bulls.
abstract: Insulin-like peptide 3 (INSL3) is a major secretory product of testicular Leydig cells. The mechanism of acute regulation of INSL3 secretion is still unknown. The present study was undertaken in pubertal beef bulls to (1) determine the temporal relationship of pulsatile secretion among LH, INSL3, and testosterone and (2) monitor acute regulation of INSL3 secretion by LH using GnRH analogue and hCG. Blood samples were collected from Japanese Black beef bulls (N = 6) at 15-minute intervals for 8 hours. Moreover, blood samples were collected at -0.5, 0, 1, 2, 3, 4, 5, and 6 hours after GnRH treatment and -0.5, 0, 2, 4, and 8 hours on the day of treatment (Day 0), and Days 1, 2, 4, 8, and 12 after hCG treatment. Concentrations of LH, INSL3, and testosterone determined by EIAs indicated that secretion in the general circulation was pulsatile. The frequency of LH, INSL3, and testosterone pulses was 4.7 ± 0.9, 3.8 ± 0.2, and 1.0 ± 0.0, respectively, during the 8-hour period. Seventy percent of these INSL3 pulses peaked within 1 hour after a peak of an LH pulse had occurred. The mean increase (peak per basal concentration) of testosterone pulses was higher (P < 0.001) than that of INSL3 pulses. After GnRH treatment, LH concentrations increased (P < 0.01) dramatically 1 hour after treatment and remained high (P < 0.05) until the end of sampling, whereas an elevated (P < 0.05) INSL3 concentration occurred at 1, 2, 5, and 6 hours after treatment. Testosterone concentrations increased (P < 0.01) 1 hour after the treatment and remained high until the end of sampling. After hCG treatment, an increase of INSL3 concentration occurred at 2 and 4 hours, and Days 2, 4, and 8 after treatment (P < 0.05), whereas in case of testosterone, concentrations remained high (P < 0.01) until Day 8 after treatment. The increase (maximum per pretreatment concentration) of INSL3 concentrations after injecting GnRH or hCG was much lower (P < 0.001) than that of testosterone. In conclusion, secretion of INSL3 in blood of bulls occurred in a pulsatile manner. We inferred an acute regulation of INSL3 by LH in bulls because INSL3 concentrations increased immediately after endogenous and exogenous LH stimulation. The increase of INSL3 concentrations by LH was much lower than that of testosterone in bulls.
authors: Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan.
authors: M A
authors: MA
authors: Hannan
authors: Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan.
authors: Y
authors: Y
authors: Fukami
authors: Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan. Electronic address: nkawate@vet.osakafu-u.ac.jp.
authors: N
authors: N
authors: Kawate
authors: Northern Center of Agricultural Technology, General Technological Center of Hyogo Prefecture for Agriculture, Forest and Fishery, Wadayama, Hyogo, Japan.
authors: M
authors: M
authors: Sakase
authors: Northern Center of Agricultural Technology, General Technological Center of Hyogo Prefecture for Agriculture, Forest and Fishery, Wadayama, Hyogo, Japan.
authors: M
authors: M
authors: Fukushima
authors: Department of Animal Science, Faculty of Agriculture, University of Ruhuna, Kamburupitiya, Sri Lanka.
authors: I N
authors: IN
authors: Pathirana
authors: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.
authors: E E
authors: EE
authors: Büllesbach
authors: Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan.
authors: T
authors: T
authors: Inaba
authors: Department of Advanced Pathobiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan.
authors: H
authors: H
authors: Tamada
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000494:pharmacology; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism; D007986:Luteinizing Hormone / Q000235:genetics / Q000378:metabolism*; D008297:Male; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012741:Sexual Maturation / Q000502:physiology*
chemical_list: D007328:Insulin; C084797:Leydig insulin-like protein; D011506:Proteins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; C009936:fertirelin
keywords: Beef bull; GnRH; INSL3; LH; Testosterone; hCG