Abstract
Noradrenergic stimulation increases progesterone, oxytocin and prostaglandins in the bovine luteal tissue. Better understanding of noradrenaline (NA) role in bovine the corpus luteum (CL) can advance our current knowledge on the regulatory mechanism of CL function. The present study was conducted to explore the source of noradrenaline and further to investigate whether nerve growth factor (NGF), insulin like growth factor 1 (IGF1) and transforming growth factor β1 (TGFβ1) influence the expression of dopamine-β-hydroxylase (DBH), biosynthetic enzyme of NA in cultured bovine luteal cells. Corpora lutea were collected and classified into stages of early, developing, mid, late, and regressed. Messenger RNA (mRNA) and protein expression of DBH were studied throughout the estrous cycle. Additionally, DBH protein expression was examined in cultured mid luteal cells after tumour necrosis factor alpha/interferon gamma (TNFα/IFNγ)-induced apoptosis or after treatment with NGF, IGF1, and TGFβ1. DBH mRNA and protein expressions were detected throughout the cycle without significant changes in the protein level while mRNA showed a decrease at the developing stage (P < 0.05). Interestingly, NGF, IGF1, and TGFβ1 increased DBH expression in cultured luteal cells (P < 0.05). The overall findings suggest non-neural source of noradrenaline in the bovine CL which appears to be regulated by NGF, IGF1, and TGFβ1 indicating intraluteal molecules play an important and unrecognized role in the CL function.
Highlights
The corpus luteum (CL) lifespan and function are regulated by luteotropic and luteolytic hormones, growth factors, cytokines, and neurotransmitters
We investigated the effect of tumour necrosis factor alpha/ interferon gamma (TNFα/IFNγ)-induced apoptosis on DBH protein expression in cultured luteal cells in order to clarify whether luteal regression would influence the expression of DBH
To explore whether locally synthesized NA is regulated by growth factors, we examined the effects of growth factors such as nerve growth factor (NGF) insulin-like growth factor (IGF1) and transforming growth factor (TGFβ1) on DBH protein expression in cultured mid luteal cells
Summary
The corpus luteum (CL) lifespan and function are regulated by luteotropic and luteolytic hormones, growth factors, cytokines, and neurotransmitters (see reviews, Niswender et al 2000; Kotwica et al 2002; Schams & Barisha 2004). Neurotransmitters are believed to play a special role in the neuron-endocrinotrophic stimulatory complex in the ovary (Tsafriri & Adashi 1994). Better understanding of noradrenaline (NA) role in the CL is physiologically important and can advance our current knowledge on the regulatory mechanism of CL function. The ovarian source of catecholamines is believed to be originated from sympathetic nerve fibers or from the adrenal gland via the blood stream. Since the bovine ovary is innervated by networks of adrenergic nerves which are located in close vicinity to primordial and primary follicles and around the blood vessels (Kaleczyc et al 1995). There is no direct evidence to show that the bovine CL is capable of de novo synthesis of catecholamines, or that it has the ability to take up and retain NA from ovarian sympathetic neurons, fibers or the peripheral circulation. The lack of information on the source of endogenous NA raises question to its physiological significance in luteal progesterone and oxytocin stimulation in vivo and in vitro (Kotwica et al 1991, 1994)
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