Vasoactive intestinal peptide modulates luteinizing hormone subunit gene expression in the anterior pituitary in female rat.
ABSTRACT The direct monosynaptic pathway which exists between vasoactive intestinal peptide (VIP) and GnRH neurons in the hypothalamic preoptic area provides a neuroanatomical background for the modulatory effects of VIP exerted on GnRH neurons activity. Though central microinjection of VIP revealed its involvement in the modulation of LH release pattern, there is a lack of data concerning a possible VIP influence on the alpha and LHbeta subunit gene expression in the pituitary gland. Using a model based on intracerebroventricular pulsatile peptide(s) microinjections (1 pulse/h [10 microl/5 min] over 5 h) the effect of exogenous VIP (5 nM dose) microinjection on subunits mRNA content in ovariectomized/oestrogen-pretreated rats was studied. Subsequently, to obtain data concerning the involvement of GnRH and VIP receptor(s) in the regulation of alpha and LHbeta subunit mRNA expression, OVX/estrogen-primed rats received a pulsatile microinjections of 5 nM VIP with 3 nM antide (GnRH receptor antagonist) or 5 nM VIP with 15 nM VIP 6-28 (VIP receptor antagonist). In this case, substances were given separately with a 30 min lag according to which each antagonist pulse preceded a VIP pulse. Northern-blot analysis revealed that VIP microinjection resulted in a decreased alpha and LHbeta mRNA content in pituitary gland and this effect was dependent on GnRH receptor activity. Moreover, obtained results indicated that centrally administered VIP might operate through its own receptor(s) because a receptor antagonist, VIP 6-28, blocked the inhibitory effect of VIP exerted on both LH subunit mRNA content and LH release.
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ABSTRACT: Epithelial ovarian cancer, which accounts for 80-90% of all ovarian cancers, is the most common cause of death from gynecological malignancies and is believed to originate from the ovarian surface epithelium. In the present study we investigated the expression of GnRH and its receptor in human ovarian surface epithelial (hOSE) cells and provided novel evidence that GnRH may have antiproliferative effects in this tissue. Using RT-PCR and Southern blot analysis, we cloned the GnRH and GnRH receptor (GnRHR) in hOSE cells. Sequence analysis revealed that GnRH and its receptor have sequences identical to those found in the hypothalamus and pituitary, respectively. To address whether GnRH regulates its own and receptor messenger RNA (mRNA), the cells were treated with different concentrations of the GnRH agonist (D-Ala6)-GnRH. Expression levels of GnRH and its receptor were investigated using quantitative and competitive RT-PCR, respectively. Interestingly, a biphasic effect was observed for the GnRH and GnRHR mRNA levels. High concentrations of the GnRH agonist (10(-7) and 10(-9) M) decreased GnRH and GnRHR mRNA levels, whereas a low concentration (10(-11) M) resulted in up-regulation of GnRH and receptor mRNA levels. Treatment with the GnRH antagonist, antide, prevented the biphasic effects of the GnRH agonist in hOSE cells, confirming the specificity of the response. Furthermore, to investigate the physiological significance, we studied receptor-mediated growth regulatory effects of GnRH in human ovarian surface epithelial cells. The cells were treated with GnRH analogs, and the proliferative index of cells was measured using a [3H]thymidine incorporation assay. (D-Ala6)-GnRH had a direct inhibitory effect on the growth of hOSE cells in a time- and dose-dependent manner. This antiproliferative effect of the GnRH agonist was receptor mediated, as cotreatment of hOSE cells with antide abolished the growth inhibitory effects of the GnRH agonist. The results strongly suggest that GnRH can act as an autocrine/paracrine regulator in hOSE cells.Endocrinology 01/2000; 141(1):72-80. · 4.72 Impact Factor
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ABSTRACT: Retrograde tract tracing and immunocytochemistry were used to investigate the CNS source of the VIP that is present in high concentrations in the hypophysial portal blood and has been shown to have a stimulatory effect on pituitary prolactin secretion. Fluoro-gold (FG), which enters the CNS through areas devoid of the blood-brain barrier, such as median eminence, was injected peripherally. Brain sections from FG-treated animals were immunostained for VIP. A small population of VIP-containing cell bodies in the parvocellular and periventricular parts of the paraventricular nucleus (PVN) was also labeled with FG. Vasoactive intestinal peptide-immunoreactive perikarya not labeled with FG were also observed in the PVN, as well as FG-labeled cells that did not contain VIP. The results suggest that some VIP-producing neurons in the PVN project to the median eminence and are, therefore, functionally related to pituitary regulation; the function of other VIP neurons in the PVN is unknown.Peptides 01/1993; · 2.52 Impact Factor
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ABSTRACT: The efferent projections of the suprachiasmatic nucleus (SCh) in the rat hypothalamus have been reexamined with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L), which displays labeled axons with the clarity of a Golgi impregnation. Fibers from the SCh can be divided into six pathways for descriptive purposes. By far the densest terminal field arising from cells in the SCh ends in a roughly comma-shaped zone between the SCh and paraventricular nucleus on the one hand and the periventricular nucleus and anterior hypothalamic area on the other. A few axons continue dorsally from this "subparaventricular zone" to pass through parvicellular parts of the paraventricular nucleus and the overlying midline thalamic nuclei to end in midrostrocaudal parts of the paraventricular nucleus of the thalamus, and a larger number continue caudally to end in the dorsomedial nucleus, dorsal parts of the cell-sparse zone surrounding the ventromedial nucleus, and the posterior hypothalamic area. The other five pathways all consist of relatively small numbers of fibers and give rise to relatively sparse terminal fields. The second pathway consists of rostrally directed fibers that end in ventral parts of the medial preoptic area and anteroventral periventricular nucleus. The third consists of anterodorsally oriented fibers that pass through the medial preoptic nucleus and adjacent regions to end ventrally in the intermediate lateral septal nucleus. The fourth consists of fibers just caudal to the third group that end in the preoptic continuation of the bed nucleus of the stria terminalis, as well as in the parataenial nucleus and rostral part of the paraventricular nucleus of the thalamus. The fifth consists of laterally directed fibers that course over the optic tract to end in the ventral lateral geniculate nucleus. And the sixth consists of fibers that course posteriorally through the anterior hypothalamic and retrochiasmatic areas to end in the cell-sparse zone between the arcuate nucleus and ventral parts of the ventromedial nucleus, as well as in adjacent parts of the lateral hypothalamic area. The distribution of projections labeled following PHA-L injections centered in the subparaventricular zone was also examined and was confirmed with retrograde tracer experiments (Watts and Swanson: J. Comp. Neurol. 258:230-252, '87). The results indicate that the subparaventricular zone projects to essentially the same regions as the SCh, only much more densely, and also sends fibers back to the SCh.(ABSTRACT TRUNCATED AT 400 WORDS)The Journal of Comparative Neurology 05/1987; 258(2):204-29. · 3.66 Impact Factor