Pituitary LH responsiveness to GnRH in vitro as related to GnRH receptor number

1984 ◽  
Vol 247 (5) ◽  
pp. E651-E656 ◽  
Author(s):  
D. M. Baldwin ◽  
G. A. Bourne ◽  
J. C. Marshall
Keyword(s):  
Binding Capacity ◽  
In Vitro Study ◽  
Gnrh Receptor ◽  
Treatment Groups ◽  
Pituitary Glands ◽  
Lh Release ◽  
Receptor Number ◽  
Lh Secretion ◽  
Gnrh Infusion

The objective of this in vitro study was to determine whether the increase in the augmented phase of the biphasic luteinizing hormone (LH) response to gonadotrophin-releasing hormone (GnRH) and its enhancement by estradiol (E2) were associated with GnRH-stimulated increases in pituitary GnRH receptor concentration. Pituitary glands from 72 h ovariectomized (OVX), OVX + E2, or proestrous rats were perifused continuously with GnRH (12 ng/h). LH release was measured at 10-min intervals, and pituitary GnRH-binding capacity (GnRH-BC) was assessed at 0, 40, 80, 120, and 240 min after addition of GnRH. All treatment groups exhibited a biphasic pattern of LH release; initial (20-70 min) and augmented (120-240 min) mean rates of LH secretion (micrograms/h) were 1.78 and 3.92 (OVX), 6.40 and 16.67 (OVX + E2), and 2.79 and 18.64 (proestrus), respectively. Total LH release was significantly greater in the OVX + E2 and proestrous groups (44.0 and 45.8 micrograms) vs. the OVX group (12.4 micrograms). Throughout the GnRH infusion period, GnRH-BC did not change significantly in any of the treatment groups with the exception of the OVX group in which there was a transient small decrease at 80 min post-GnRH infusion. There were no significant differences between treatment groups in GnRH-BC at any time after infusion of GnRH. These results demonstrate that the acute and augmented phases of GnRH-stimulated LH release and the enhancement of this biphasic response by E2 occurs independent of any increase in GnRH-BC and suggest that these events are mediated by postreceptor mechanisms.

Inverse effects of activin and inhibin on the synthesis and secretion of FSH and LH by ovine pituitary cells in vitro

1991 ◽  
Vol 6 (2) ◽  
pp. 171-178 ◽  
Author(s):  
S. Muttukrishna ◽  
P. G. Knight
Keyword(s):  
In Vitro Study ◽  
Activin A ◽  
Fixed Dose ◽  
Pituitary Cells ◽  
Cell Content ◽  
Cellular Content ◽  
Lh Release ◽  
Lh Secretion ◽  
Dose Dependent

ABSTRACT Little information is available on the effects of activin and inhibin on the synthesis and secretion of pituitary gonadotrophins in species other than the rat. In this in-vitro study, ovine pituitary cell cultures derived from immature sheep were used to investigate the effects of recombinant human activin-A and native Mr 32 000 bovine inhibin on basal and gonadotrophin-releasing hormone (GnRH)-induced release of FSH and LH. Residual cellular contents of FSH and LH were also determined, allowing total content/well to be calculated. Activin-A promoted a dose-dependent increase in basal (+72%; P<0·001) and GnRH-induced (+25%; P<0·001) release of FSH as well as in the residual cell content (+114%; P<0·001) and total FSH content/well (+67%; P<0·001). Conversely, inhibin significantly (P<0·001) suppressed each aspect of FSH production examined, confirming that in sheep, as in rats, activin and inhibin exert opposing effects on pituitary FSH production. In contrast to the rat, however, in which activin is reported to have no effect on LH secretion, exposure of sheep pituitary cells to activin-A promoted a dose-dependent suppression (−42%; P<0·001) of GnRH-induced LH release. This was associated with a corresponding increase (P<0·001) in residual cellular content of LH. Consistent with a previous report from this laboratory, inhibin had the opposite effect and significantly enhanced (+47%; P<0·001) GnRH-induced LH release. This was associated with a corresponding fall (P<0·001) in residual cellular content of LH. Neither activin-A nor inhibin significantly affected total LH content/well, indicating a lack of effect of either agent on LH biosynthesis. Comparison of the dose-dependent effects of inhibin on FSH and LH production by cells cultured in the presence and absence of a fixed dose level of activin-A (5 ng/ml) revealed a significant (P<0·01) interaction between the two agents which appeared to be of a non-competitive nature. These findings support the concept that both activin and inhibin participate in the gonadal feedback control of pituitary FSH secretion in the sheep. They also indicate that both agents are capable of modulating GnRH-induced LH secretion in this species.

Hydroxyl Safflower Yellow Pigment A (HSYA) Improves Vascular Endothelial Injury Induced by Lipopolysaccharide In Vitro Study

2021 ◽  
Vol 11 (9) ◽  
pp. 1792-1798
Author(s):  
Li Yan ◽  
Ge Jingping ◽  
Yin Yuanyuan ◽  
Li Xiaomei ◽  
Zhao Boxiang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
In Vitro Study ◽  
Treated Group ◽  
Yellow Pigment ◽  
Endothelial Injury ◽  
Vitro Study ◽  
Vascular Endothelial ◽  
Treatment Groups ◽  
Dose Dependent

Aim: This research was to investigate the effects and mechanisms of HSYA in vascular endothelial injury by vitro study. Methods: Dividing HUVECs as Normal Control (NC), Model (LPS treated) group, HSYA-L, HSYA-M and HSYA-H groups. Cells in the HSYA treatment groups were treated with LPS, followed by 40 mg/ml, 80 mg/ml, and 120 mg/ml HSYA intervention (HSYA-L, HSYA-M, and HSYA -H groups), respectively. Measuring the cell proliferation, apoptosis, relative proteins and mRNA (TLR4, MyD88 and NF-κB(p65)) expressions by MTT, Flow cytometry, WB and RT-qPCR assay. Using cellular immunofluorescence to evaluate NF-κB(p65) nuclear volume of difference groups. Results: With HSYA supplement, the cell proliferation rates were significantly up-regulation with cell apoptosis significantly down-regulation with TLR4 relatived mRNA and proteins and NF-κB(p65) nuclear significantly depressed with dose-dependent (P <0.05, respectively). Conclusion: HSYA improved vascular endothelial injury induced by LPS via TLR4 pathway In Vitro.

Ionophore A23187 partially reverses LH secretory defect of pituitary cells from old rats

1987 ◽  
Vol 253 (3) ◽  
pp. E233-E237
Author(s):  
R. S. Chuknyiska ◽  
M. R. Blackman ◽  
G. S. Roth
Keyword(s):  
Primary Cultures ◽  
Extracellular Calcium ◽  
Base Line ◽  
Ionophore A23187 ◽  
Pituitary Cells ◽  
Lh Release ◽  
Old Rats ◽  
Lh Releasing Hormone ◽  
Lh Secretion

We measured in vitro release of luteinizing hormone (LH) in the presence of 1.5 mM extracellular calcium, with and without LH-releasing hormone (LHRH; 10(-10) to 10(-7) M) or the ionophore A23187 (10(-7) to 10(-4) M), in primary cultures of anterior pituitary cells from intact mature (6 mo) and old (24 mo) male and intact and ovariectomized mature and old female Wistar rats. Base-line as well as LHRH- and A23187-mediated LH secretion was decreased from cells of old rats. However, exposure to A23187 led to a nearly twofold greater augmentation of LH release from cells of old rats, thus decreasing the apparent age-related LH secretory deficit by approximately one-half. We then measured LHRH-mediated (10(-8) M) vs. A23187-mediated (10(-4) M) LH release with and without extracellular calcium (0.08-1.5 mM). For cells from both mature and old rats, there was a similar calcium dependency for A23187- and LHRH-mediated LH release, with optimal LH secretion at 1.0-1.5 mM extracellular calcium concentrations. Again, both LHRH- and A23187-stimulated LH release was significantly lower and exposure to A23187 led to a greater increase in LH release from cells of old rats. Taken together with similar findings in other systems, these data suggest that the in vitro LH secretory defect of pituitary cells from old rats results in part from one or more defects in calcium mobilization and that such alterations may be a widespread manifestation of aging.

Involvement of norepinephrine in pituitary LH release induced by oestradiol in vitro

1984 ◽  
Vol 107 (2) ◽  
pp. 199-203
Author(s):  
A. Miyake ◽  
K. Tasaka ◽  
T. Aono
Keyword(s):  
Oestrous Cycle ◽  
Female Rats ◽  
Direct Effects ◽  
Significant Release ◽  
Lh Release ◽  
Lh Secretion ◽  
Perifusion System ◽  
Double Chamber

Abstract. The direct effects of oestradiol-17β (E2) on pituitary luteinizing hormone (LH) release and the role of norepinephrine (NE) in E2-induced gonadtrophin release were examined in a sequential double chamber perifusion system by perifusing the mediobasal hypothalami (MBH) and/or pituitaries excised from normally cycling female rats. Administration of E2 induced significant release (70–160% increase, P < 0.05) of LH from the pituitary of rats in pro-oestrus, but not in other stages of the oestrous cycle. When the MBH and the pituitary were perifused in sequence, E2 induced significant release of LH in all stages of the oestrous cycle except oestrus. When the pituitary from rats in dioestrus II was perifused alone with medium containing 200 ng/ml NE, significant release of LH (80–170% increase, P < 0.05) was observed after the administration of E2. The E2-induced LH release in pro-oestrus was completely abolished by perifusion with medium containing diethyldithiocarbamate, an inhibitor of NE synthesis. These findings suggest that NE may be involved in changes of pituitary responsiveness in LH secretion to oestrogen during the rat oestrous cycle.

Oxytocin modulates the luteinizing hormone response of the rat anterior pituitary to gonadotrophin-releasing hormone in vitro

1995 ◽  
Vol 145 (1) ◽  
pp. 113-119 ◽  
Author(s):  
J J Evans ◽  
S J Hurd ◽  
D R Mason
Keyword(s):  
Luteinizing Hormone ◽  
Anterior Pituitary ◽  
The Self ◽  
Female Rats ◽  
Hormone Response ◽  
Priming Process ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Secretion

Abstract Although GnRH is believed to be the primary secretagogue for LH, oxytocin has also been shown to stimulate LH release from the anterior pituitary. We investigated the possibility that the two secretagogues interact in the modulation of LH release. Anterior pituitaries were removed from adult female rats at pro-oestrus, and tissue pieces were pre-incubated in oxytocin for 3 h prior to being stimulated with 15 min pulses of GnRH. LH output over the 1 h period from the beginning of the GnRH pulse was determined. Control incubations were carried out in the absence of oxytocin, and background secretory activities without GnRH stimulation were also determined. Tissue which was pre-exposed to oxytocin (0·012–1·25 μm) had an increased LH response to GnRH (1·25 nm). The increase was larger than the sum of the LH outputs obtained with oxytocin and GnRH separately, revealing that oxytocin synergistically enhanced LH secretion elicited by GnRH (P<0·05; ANOVA). If stimulation by GnRH was delayed for 2 h after incubation with oxytocin, an increase in LH secretion was still observed, indicating that oxytocin-induced modulation did not rapidly disappear. Oxytocin pre-incubation was observed to result in an increase of maximal GnRH-induced LH output (P<0·001; t-test), as well as an increase of intermediate responses. The LH response of the anterior pituitary to subsequent pulses of GnRH was modified by the self-priming process. The effect of oxytocin pretreatment on the response of primed tissue to GnRH was also investigated. It was found that pre-incubation in oxytocin also enhanced the LH response of primed tissue to GnRH. The study has revealed that oxytocin increases the LH output of anterior pituitary tissue in response to GnRH. The effect occurs on both GnRH-primed and unprimed tissues. The results suggest that oxytocin has the potential to regulate the dynamics of the pro-oestrous LH surge. Journal of Endocrinology (1995) 145, 113–119

scholarly journals Taurocholic acid adsorption during non-starch polysaccharide fermentation: an in vitro study

1995 ◽  
Vol 74 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Ingrid C. Gelissen ◽  
Martin A. Eastwood
Keyword(s):  
Wheat Bran ◽  
Volatile Fatty Acids ◽  
Binding Capacity ◽  
In Vitro Study ◽  
Total Radioactivity ◽  
Taurocholic Acid ◽  
Supernatant Fraction ◽  
Bile Acid Binding ◽  
Highly Correlated

The association of radiolabelled taurocholic acid with the solid fraction of a faecal fermentation mixture was measured. A human faecal inoculum was incubated with [24-14C]taurocholic acid and several non-starch polysaccharide sources (pectin, wheat bran, ispaghula (Plantago ovata) husk and seed), glucose or a substrate-free control. Portions of fermentation mixture were taken at 0, 3, 6, 21 and 24 h and centrifuged to acquire a supernatant fraction and a pellet containing the fermentation residue. 14C was measured in supernatant fractions and pellets at all time points. Volatile fatty acids (VFA) were measured at 0 and 24 h to confirm bacterial growth. Radioactivity in the pellet increased over time for all substrates. Glucose resulted in the greatest incorporation of taurocholic acid into the pellet, followed by pectin. At 24 h the proportion of the total radioactivity found in the pellet was 92% for glucose, 79% for pectin, 60% for wheat bran, 59% for ispaghula seed, 53% for ispaghula husk and 26% for the control (mean of duplicates). Glucose and pectin produced the greatest quantity of VFA at 24 h. VFA production was highly correlated with radioactivity in the pellet (r 0·976, P <0·005). These results suggest that the bile acid binding capacity of a faecal culture mixture may be strongly influenced by the fermentability of the available substrate and hence related to bacterial metabolic activity.

scholarly journals Effect of a carbamide peroxide bleaching gel containing calcium or fluoride on human enamel surface microhardness

2005 ◽  
Vol 16 (2) ◽  
pp. 103-106 ◽  
Author(s):  
Rogério de Oliveira ◽  
Adriana Franco Paes Leme ◽  
Marcelo Giannini
Keyword(s):  
Artificial Saliva ◽  
In Vitro Study ◽  
Enamel Surface ◽  
Control Group ◽  
Carbamide Peroxide ◽  
Surface Microhardness ◽  
Treatment Groups ◽  
Peroxide Bleaching ◽  
Human Enamel

This in vitro study evaluated the surface microhardness of human enamel submitted to bleaching with 10% carbamide peroxide (CP) containing calcium or fluoride. Ninety-eight dental blocks (5 x 5 mm²) with polished enamel surfaces were randomly assigned to 7 treatment groups (n=14), as follows: without bleaching and storage in artificial saliva (control); 10% CP; 10% CP + 0.05% calcium; 10% CP + 0.1% calcium; 10% CP + 0.2% calcium; 10% CP + 0.2% fluoride; and 10% CP + 0.5% fluoride. During 14 days, enamel surfaces were daily exposed to a 6-h bleaching regimen followed by storage in artificial saliva. Surface microhardness was measured before (baseline), during (7th day), immediately after bleaching (14th day) and 1 week post bleaching. Data were analyzed by two-way ANOVA and Tukey's test (p<0.05). All treatments reduced SM significantly during the bleaching cycle (7th day), immediately after bleaching (14th day) and 1 week post bleaching, compared to baseline and to the unbleached control group. In conclusion, in spite of the addition of calcium and fluoride, all bleaching treatments affected the enamel surface microhardness.

Effects of the opioid antagonist naloxone on release of luteinizing hormone in mares during the anovulatory season

1994 ◽  
Vol 142 (1) ◽  
pp. 139-144 ◽  
Author(s):  
C Aurich ◽  
S Schlote ◽  
H-O Hoppen ◽  
E Klug ◽  
H Hoppe ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Anterior Pituitary ◽  
Reproductive Activity ◽  
Endogenous Opioids ◽  
Opioid Antagonist ◽  
Lh Release ◽  
Lh Secretion ◽  
Opioid Systems ◽  
Follicular Activity

Abstract To investigate an involvement of endogenous opioids in the regulation of circannual changes in reproductive activity, effects of the opioid antagonist naloxone on the concentration of immunoreactive and bioactive luteinizing hormone (LH) in plasma were measured in mares during the anovulatory season. Naloxone (0·5 mg/kg i.v.) caused a significant increase (P<0·05) in immunoreactive as well as bioactive LH concentration in plasma. The amplitude of the increase in LH concentrations measured with an in vitro bioassay was more pronounced than the amplitude of the increase in LH secretion determined by radioimmunoassay. This indicates that although in seasonal anovulatory mares the bioactivity of LH in plasma is low, highly bioactive LH is present in the anterior pituitary and can be released by naloxone. The LH response to naloxone did not depend on the degree of ovarian follicular activity. It can be concluded that a tonic opioid inhibition of LH release is present in mares during at least part of the anovulatory season and that endogenous opioids seem to be involved in the regulation of seasonal reproductive activity in the horse. In contrast to the situation during the breeding season, the opioid systems regulating LH release are activated independently of luteal progesterone. Journal of Endocrinology (1994) 142, 139–144

scholarly journals An In Vitro Study of LH Release, Synthesis and Heterogeneity in Pituitaries from Proestrous and Short-term Ovariectomized Rats1

1986 ◽  
Vol 34 (2) ◽  
pp. 304-315 ◽  
Author(s):  
David M. Baldwin ◽  
Robert F. Highsmith ◽  
Jacques W. Ramey ◽  
Lynne A. Krummen
Keyword(s):  
In Vitro Study ◽  
Vitro Study ◽  
Short Term ◽  
Lh Release
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