Neuroendocrine Regulation of Luteinizing Hormone ıcretion in Beef Calves1

Anderson, Lloyd L.; Hard, D.L.; Carpenter, L.S.; Awotwi, E.K.; Diekman, M A

doi:10.1095/biolreprod24.4.795

Cited by 22 publications

(10 citation statements)

References 9 publications

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“…This mode of LH secretion is thought to result from pulsatile release of LHRH from the hypothalamus (Carmel, Araki & Ferin, 1976;Lincoln & Fraser, 1979;Schanbacher, D'Occhio & Kinder, 1982). Additional evidence is pro¬ vided by the low non-pulsatile LH patterns observed in calves with stalk sections (Anderson, Hard, Carpenter et al 1981). In contrast to the chronically castrated bull all steroid treatments applied to the acutely castrated animals in the present study blocked pulsatile secretion and reduced mean LH con¬ centrations.…”

Section: Discussionsupporting

confidence: 48%

Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull

Gettys¹,

D’Occhio²,

Henricks³

et al. 1984

Journal of Endocrinology

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Twenty acutely castrated bulls were used to investigate the role of androgenic and oestrogenic steroids in the feedback control of LH secretion. The effects of 5 alpha-dihydrotestosterone (DHT) or the growth stimulants trenbolone acetate (TBA) or oestradiol-17 beta (OE2) on serum LH secretory profiles were measured. In addition, pituitary LH responses to exogenous LH releasing hormone (LHRH) were determined to differentiate between hypothalamic and pituitary sites of steroid action. At the time of castration, two groups of animals were given implants of either 45 mg OE2 or 200 mg TBA. Another group received equivalent to 30 mg daily injections of DHT. Control steers showed an increase in LH from 2.4 +/- 0.5 (S.E.M.) micrograms/l to 7.0 +/- 0.5 micrograms/l during the week after castration. Treatment with DHT and TBA prevented the post-castration rise in serum LH. In contrast, steers given implants of OE2 showed a significantly greater increase in LH than controls 1 day after castration, but by day 5 LH declined in the OE2-treated group to precastration values. Five weeks after castration control steers secreted LH in pulses at intervals of 40-50 min and with an amplitude of 4.2 +/- 0.4 micrograms/l. Pulses were not detected in the LH profiles of the steroid-treated steers. Dihydrotestosterone and TBA significantly reduced pituitary LH responses to exogenous LHRH, whereas steers receiving OE2 showed LH responses to LHRH which were similar to those observed in castrated controls. These results support the hypothesis that androgenic and oestrogenic components participate separately in the feedback control of LH secretion in the bull.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussionsupporting

confidence: 48%

Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull

Gettys¹,

D’Occhio²,

Henricks³

et al. 1984

Journal of Endocrinology

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“…Administration of central nervous system depressants to female pigs and rats (Kesner et al, 1987;Kimura et al, 1995), electro-lesion of the hypophysiotropic area in female rhesus monkeys and ewes (Jackson et al, 1978), or interruption of hypophyseal blood circulation in female rhesus monkeys (Ferin et al, 1974), beef calves (Anderson et al, 1981) and female pigs (current study) eliminates pulsatile LH secretion. This pulsatile pattern reflects a basic rhythm of the secretory neurons of the hypophysiotropic area in the hypothalamus that secretes LHRH into hypophyseal portal vessels for transport to the adenohypophysis (Hotchkiss and Knobil, 1994;Terasawa et al, 1999).…”

Section: Discussionmentioning

confidence: 76%

Luteinizing hormone secretion as affected by hypophyseal stalk transection and estradiol-17β in ovariectomized gilts

Ford

Berardinelli

Christenson

et al. 2000

Animal Reproduction Science

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The objectives were to determine hypothalamic regulation of pulsatile luteinizing hormone (LH) secretion in female pigs and the biphasic feedback actions of estradiol-17beta (E(2)-17beta). In the first study, the minimum effective dosage of E(2)-17beta that would induce estrus in ovariectomized gilts was determined to be 20microg/kg body weight. In the second study, ovariectomized gilts were assigned randomly on day 0 to treatments: (a) hypophyseal stalk transection (HST), (b) cranial sham-operated control (SOC), and (c) unoperated control (UOC). On day 3, gilts from each group received a single i.m. injection of either E(2)-17beta (20microg/kg body weight) or sesame oil. Blood was collected from an indwelling jugular cannula at 15min intervals for 3h before (day -2) and after treatment (day 2) from HST, SOC and UOC gilts. On day 3, blood was collected at 2h intervals for 12h after E(2)-17beta or sesame oil injection and at 4h intervals thereafter for 108h. Pulsatile LH secretion in all gilts 2 days after ovariectomy exhibited a frequency of 0.9+/-0.06peaks/h, amplitude of 1.3+/-0.13ng/ml, baseline of 0.8+/-0.07. Serum LH concentrations from SOC and UOC gilts were similar on day 2 and profiles did not differ from those on day -2. In HST gilts pulsatile LH release was abolished and mean LH concentration decreased compared with controls (0 versus 0.9+/-0. 06peaks/h and 0.77+/-0.03 versus 1.07+/-0.07ng/ml, respectively; P<0. 05). E(2)-17beta or sesame oil did not affect serum LH concentration in HST gilts, and LH remained constant throughout 120h (0.7+/-0. 07ng/ml). In SOC and UOC control gilts, E(2)-17beta induced a 60% decrease (P<0.05) in LH concentration within 12h, and LH remained low until 48h, then increased to peak values (P<0.05) by 72h, followed by a gradual decline to 120h. Although pituitary weight decreased 31% in HST gilts compared with controls (228 versus 332mg, P<0.05), an abundance of normal basophils was evident in coronal sections of the adenohypophysis of HST comparable to that seen in control gilts. The third and fourth studies determined that hourly i. v. infusions of LHRH (2microg) and a second injection of E(2)-17beta 48h after the first had no effect on the positive feedback action of estrogen in UOC. However, in HST gilts that received LHRH hourly, the first injection of E(2)-17beta decreased (P<0.05) plasma LH concentrations while the second injection of E(2)-17beta failed to induce a positive response to estrogen. These results indicate that both pulsatile LH secretion and the biphasic feedback action of E(2)-17beta on LH secretion depend on hypothalamic regulatory mechanisms in the gilts. The isolated pituitary of HST gilts is capable of autonomous secretion of LH; E(2)-17beta will elicit direct negative feedback action on the isolated pituitary gland if the gonadotropes are supported by exogenous LHRH, but E(2)-17beta at high concentrations will not induce positive feedback in isolated pituitaries. Thus, the direct effect of E(2)-17beta on the pituitary of monkeys cannot be mimicked in...

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“…Thereafter, depressed growth rates, lack of onset of pubertal estrus, and decreased PRL blood concentration result in HST calves compared with SOC animals (38,39). Regardless, basal PRL serum concentration responds to seasonal changes, peaking in summer and exhibiting a nadir in winter, in both HST and SOC calves (40,41).…”

Section: Discussionmentioning

confidence: 99%

Long-Term Growth after Hypophyseal Stalk Transection and Hypophysectomy of Beef Calves

Anderson

1999

Endocrinology

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Hypothalamic hormones regulate episodic and basal secretion of hormones from the anterior pituitary gland that affect metabolism and growth in cattle. This study focused on long-term growth in young calves subjected to hypophysectomy (HYPOX), hypophyseal stalk transection (HST), and sham operation control (SOC). Cross-bred (Hereford x Aberdeen Angus) and Hereford, and Aberdeen Angus calves were HYPOX (n ϭ 5), HST (n ϭ 5), or SOC (n ϭ 8) at 146 Ϯ 2 days of age, whereas another group was HST (n ϭ 5) or SOC (n ϭ 7) at 273 Ϯ 5 days of age. Body weight was determined every 21 days from birth to 1008 days of age. Anterior vena cava blood was withdrawn at 4-day intervals from day 64 -360 for RIA of GH, TSH, T 4 , T 3 , and LH, and at 20-min intervals for 480 min to determine episodic hormone secretion. Daily feed intake was determined in HST and SOC calves during an 80-day period. Birth weight averaged 35 Ϯ 1 kg (Ϯ SE) and was 142 Ϯ 4 kg at 126 days and 208 Ϯ 8 kg at 252 days before surgery. From day 146-1008, growth was arrested (P Ͻ 0.001) in HYPOX (0.06 Ϯ 0.01 kg/day) compared with SOC (0.50 Ϯ 0.04 kg/day) calves. Growth continued but at a significantly lower rate (P Ͻ 0.05) in calves HST at 146 days (0.32 Ϯ 0.07 kg/day) and 273 days (0.32 Ϯ 0.06 kg/day) compared with SOC (0.50 Ϯ 0.09 kg/day). Growth continued to be impaired to 1008 days, but more so in those HST at 146 days (432 Ϯ 43 kg BW) than 273 days (472 Ϯ 5 kg BW) and less (P Ͻ 0.05) than SOC (586 Ϯ 37 kg BW). Daily feed intake was consistently less (P Ͻ 0.05) in HST compared with SOC calves. Although episodic GH secretion was abolished and peripheral serum GH concentration remained consistently lower in HST (2.4 ng/ml) than SOC (5.5 ng/ml; P Ͻ 0.01), the calves continued to grow throughout 1008 days. Peripheral serum TSH concentration was less (P Ͻ 0.05) HST compared with SOC calves. There was an abrupt decrease (P Ͻ 0.001) in serum T 4 (4-fold) and T 3 (3-fold) concentration after surgery that remained to 360 days in HST compared with SOC calves. At the time calves were killed, pituitary gland weight was markedly reduced (P Ͻ 0.001) in HST (0.18 Ϯ 0.01 g/100 kg BW) compared with SOC (0.54 Ϯ 0.03 g/100 kg BW). Histological examination of pituitary glands from HST calves indicated the persistence of secretory GH and TSH cells in the same areas of the adenohypophysis as SOC calves. Coronal sections of the gland stained with performic acid-Alcian blue-periodic acid-Schiff-orange G, revealed GH and TSH secreting cells in HST calves similar to controls. These results indicate that long-term growth continues, but at a slower rate, after hypophyseal stalk transection of immature calves in spite of complete abolition of episodic GH secretion and consistently decreased basal secretion of GH, TSH, T 4 , and T 3 compared with sham-operated animals. Growth was abolished after hypophysectomy of immature calves in which circulating GH and TSH was undetectable. (Endocrinology 140: [2405][2406][2407][2408][2409][2410][2411][2412][2413][2414] 1999)

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Neuroendocrine Regulation of Luteinizing Hormone ıcretion in Beef Calves1

Abstract: ABSTRACT

Cited by 22 publications

References 9 publications

Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull

Suppression of LH secretion by oestradiol, dihydrotestosterone and trenbolone acetate in the acutely castrated bull

Luteinizing hormone secretion as affected by hypophyseal stalk transection and estradiol-17β in ovariectomized gilts

Long-Term Growth after Hypophyseal Stalk Transection and Hypophysectomy of Beef Calves

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