L-Dopa Effects on Serum LH and Prolactin in Old and Young Female Rats

Watkins, Bruce E.; McKay, Donald W.; Meites, Joseph; Riegle, Gail D.

doi:10.1159/000122454

Cited by 22 publications

(3 citation statements)

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“…Prolactin levels were measured in conditioned media from anterior pituitaries incubated in the presence or absence of L-Dopa. Treatment with L-Dopa is known to suppress PRL circulating levels in laboratory animals (39)(40)(41)(42)(43) and in Parkinson's (44,45) or non-parkinsonian patients (46,47). These in vivo effects could be produce at hypothalamic and/or anterior pituitary levels.…”

Section: Accepted Articlementioning

confidence: 99%

Anterior pituitary gland synthesises dopamine from l‐3,4‐dihydroxyphenylalanine (l‐dopa)

Orrillo

Dios

Asad

et al. 2020

J Neuroendocrinology

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Prolactin (PRL) is a hormone principally secreted by lactotrophs of the anterior pituitary gland. Although the synthesis and exocytosis of this hormone are mainly under the regulation of hypothalamic dopamine (DA), the possibility that the anterior pituitary synthesizes this catecholamine remains unclear. In this study, our aim was to determine if the anterior pituitary produces DA from the precursor L-Dopa. To this purpose, we studied the expression of aromatic L-amino acid decarboxylase (AADC) enzyme and the transporter VMAT2 in the anterior pituitary, AtT20 and GH3 cells by immunofluorescence and western blot. Moreover, we investigated the production of DA Accepted Article This article is protected by copyright. All rights reserved from L-Dopa and its release in vitro. Then, we explored the effects of L-Dopa in the secretion of PRL from anterior pituitary fragments. We observed that the anterior pituitary, AtT20 and GH3 cells express both AADC and VMAT2. Next, we detected an increase in DA content after anterior pituitary fragments were incubated with L-Dopa. Also, the presence of L-Dopa increased DA levels in incubation media and reduced PRL secretion. Likewise, the content of cellular DA increased after AtT20 cells were incubated with L-Dopa. In addition, L-Dopa reduced CRH-stimulated ACTH release from these cells after AADC activity was inhibited by NSD-1015. Moreover, DA formation from L-Dopa increased apoptosis and decreased proliferation. However, in the presence of NSD-1015, L-Dopa decreased apoptosis and increased proliferation rates. These results suggest that the anterior pituitary synthesizes DA from L-Dopa by AADC and this catecholamine can be released from this gland contributing to the control of PRL secretion. In addition, our results suggest that L-Dopa exerts direct actions independently from its metabolization to DA.

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Section: Accepted Articlementioning

confidence: 99%

Anterior pituitary gland synthesises dopamine from l‐3,4‐dihydroxyphenylalanine (l‐dopa)

Orrillo

Dios

Asad

et al. 2020

J Neuroendocrinology

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“…For example, a loss of the LH surge, which is necessary to maintain cycles, has been attributed to a loss in hypothalamic catecholaminergic (norepinephrine and dopamine) function with age (Wise, 1984; Mohankumar et al, 1995). If the female rodent is treated with catecholaminergic agonists such as l ‐tyrosine (e.g., rat; Watkins et al, 1975; Cooper and Walker, 1979; Forman et al, 1980) or L ‐dopa (e.g., rat; Quadri et al, 1973; or mouse; Cotzias et al, 1977; Flurkey et al, 1987), the ovulatory surge of LH and ovarian cycles are maintained and reproductive senescence is delayed. In these studies, the effects of catecholamine treatment on LH secretion and subsequent ovarian function were the primary focus.…”

Section: Reproductive Aging and Mammary Tumorsmentioning

confidence: 99%

Atrazine and reproductive function: mode and mechanism of action studies

Cooper

Laws

Das

et al. 2007

Birth Defects Research Pt B

155

102

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Atrazine, a chlorotriazine herbicide, is used to control annual grasses and broadleaf weeds. In this review, we summarize our laboratory's work evaluating the neuroendocrine toxicity of atrazine (and related chlorotriazines) from an historic perspective. We provide the rationale for our work as we have endeavored to determine: 1) the underlying reproductive changes leading to the development of mammary gland tumors in the atrazine-exposed female rat; 2) the cascade of physiological events that are responsible for these changes (i.e., the mode of action for mammary tumors); 3) the potential cellular mechanisms involving adverse effects of atrazine; and 4) the range of reproductive alterations associated with this pesticide.

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“…We and others have reported low basal serum LH levels in aged male rats (6,9) and in aged female rats in various reproductive states (7,11). A recent report suggests that serum LH levels during the proestrous surge are reduced in 12 mo cycling rats compared to 3-5 mo old cycling rats (12).…”

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confidence: 66%

Serum LH Levels Following Multiple LHRH Injections in Aging Rats

Miller

Riegle

1978

Experimental Biology and Medicine

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Reduced reproductive function is characteristic of aging in mammalian species. Although the precise neuroendocrine mechanisms involved with age-related alterations in reproduction remain unresolved, current information suggests that age may affect several components of the hypothalamic-hypophyseal-gonadal control system.Recent studies have shown reduced serum testosterone levels in aged male rats and humans (1, 2). Ovarian steroid production also changes in aged rats. Normal ovarian cyclicity is replaced by periods of constant estrous and repetitive pseudopregnancies (3). The effects of age on gonadal hnction are related to the effects of aging on gonadotropin secretion. Although the reduction in gonadal steroid production with age in humans is accompanied by increased blood gonadotropin concentrations (4, 9, there is no evidence for similar increases in gonadotropin release accompanying the reduced gonadal steroid secretion in aged rats. We recently reported decreased serum LH levels in aged male rats (6). In female rats the effect of age on serum LH levels is variable and related to the variable ovarian states of the aged rat. Although aged constant estrous rats have higher serum LH concentrations than do young cycling female rats in estrous or diestrous stages of their ovarian cycles, the LH level in the aged rats is noncyclic and is much less than that found in young rats at proestrus (7). This study also showed that aged rats with repetitive pseudopregnancies or aged anestrous rats have serum LH levels which are lower than LH levels in young rats at diestrus. Additional studies have shown that ovaries from young rats grafted into aged female rats resume the Supported in part by Grant No. AG-00441 from the National Institute of Aging. Published with the approval of the Michigan State University Agriculture Experiment Station as Journal Article No. 8370. endocrine state of the recipient before the transplant (3).These studies suggest significant age effects on pituitary gonadotropin secretion. In most reproductive states old rats have decreased serum LH levels. These low LH concentrations suggest chronically reduced pituitary LH secretion. In addition we have reported smaller increases in serum LH following intravenous LH releasing hormone (LHRH) injections in aged compared to young rats of both sexes (6, 7). The increase in serum LH following acute LHRH injection in aged rats indicates that their pituitaries are capable of secreting greater amounts of LH than they normally maintain. The long-term reduced LH secretory activity which is characteristic of the aged rat could at least partially account for our reported decrease in pituitary responsiveness to actue LHRH in these animals. The current study was designed to consider the effects of more sustained LHRH stimulation on serum LH concentration in aging laboratory rats.Materials and methods. The rats used in these studies were on the Long-Evans strain. Young adult animals were 4 and 5 mo of age, the aged groups ranged from 24 to 28 mo of age. The aged female...

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L-Dopa Effects on Serum LH and Prolactin in Old and Young Female Rats

Cited by 22 publications

References 4 publications

Anterior pituitary gland synthesises dopamine from l‐3,4‐dihydroxyphenylalanine (l‐dopa)

Anterior pituitary gland synthesises dopamine from l‐3,4‐dihydroxyphenylalanine (l‐dopa)

Atrazine and reproductive function: mode and mechanism of action studies

Serum LH Levels Following Multiple LHRH Injections in Aging Rats

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