Effects of interleukins on secretion of luteinizing hormone from ovine pituitary cells

T. D. Braden From the Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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C. Fry From the Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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J. L. Sartin From the Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

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 MS, PhD

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Abstract

Objective

To determine whether cytokines of homologous species might mediate the stimulatory effects of endotoxin on release of luteinizing hormone (LH) from pituitary cells.

Sample Population

Cells from pituitary glands collected from 8- to 14-month-old wethers.

Procedure

Cells from the anterior pituitary gland were cultured in the presence of recombinant ovine or bovine cytokines (interleukin [IL]-1α, IL-1β, and IL-2), tumor necrosis factor-α (TNF), and interferon-γ (IFN-γ). Luteinizing hormone that was released into the medium was measured. Cells were also cultured with modulators of signal transduction pathways to evaluate the second messenger system used by IL-1α and IL-1β.

Results

Similar to effects of endotoxin, IL-1α and IL-1β stimulated release of LH. Interleukin 2, TNF, and IFN-γ did not have a detectable effect on release of LH. Stimulation of LH release by IL-1αand IL-1β required activation of voltage-dependent Ca2+ channels and appeared to involve protein kinase C.

Conclusions

IL-1αand IL-1β may mediate the direct stimulatory effect of endotoxin on release of LH in vitro. Interleukin 2, TNF, and IFN-γ do not have a direct effect on release of LH; therefore, they do not mediate this effect of endotoxin.

Clinical Relevance

Stressors, including infection, are often associated with reduced fertility. Infection resulting in endotoxin release, production of interleukins, or both, can lead to direct stimulation of LH release from the pituitary gland. Inopportune release of LH via cytokines may interfere with normal pulsatile release of LH, thereby suppressing gonadal function. (Am J Vet Res 1998;59:1488–1493)

Abstract

Objective

To determine whether cytokines of homologous species might mediate the stimulatory effects of endotoxin on release of luteinizing hormone (LH) from pituitary cells.

Sample Population

Cells from pituitary glands collected from 8- to 14-month-old wethers.

Procedure

Cells from the anterior pituitary gland were cultured in the presence of recombinant ovine or bovine cytokines (interleukin [IL]-1α, IL-1β, and IL-2), tumor necrosis factor-α (TNF), and interferon-γ (IFN-γ). Luteinizing hormone that was released into the medium was measured. Cells were also cultured with modulators of signal transduction pathways to evaluate the second messenger system used by IL-1α and IL-1β.

Results

Similar to effects of endotoxin, IL-1α and IL-1β stimulated release of LH. Interleukin 2, TNF, and IFN-γ did not have a detectable effect on release of LH. Stimulation of LH release by IL-1αand IL-1β required activation of voltage-dependent Ca2+ channels and appeared to involve protein kinase C.

Conclusions

IL-1αand IL-1β may mediate the direct stimulatory effect of endotoxin on release of LH in vitro. Interleukin 2, TNF, and IFN-γ do not have a direct effect on release of LH; therefore, they do not mediate this effect of endotoxin.

Clinical Relevance

Stressors, including infection, are often associated with reduced fertility. Infection resulting in endotoxin release, production of interleukins, or both, can lead to direct stimulation of LH release from the pituitary gland. Inopportune release of LH via cytokines may interfere with normal pulsatile release of LH, thereby suppressing gonadal function. (Am J Vet Res 1998;59:1488–1493)

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