scholarly journals Regulation of gonadotrophin secretion by inhibin, testosterone and gonadotrophin-releasing hormone in pituitary cell cultures of male monkeys

1998 ◽  
Vol 159 (1) ◽  
pp. 103-110 ◽  
Author(s):  
U Fingscheidt ◽  
GF Weinbauer ◽  
HL Fehm ◽  
E Nieschlag
Keyword(s):  
Dose Response ◽  
Pituitary Cells ◽  
Basal Secretion ◽  
Response Curves ◽  
Gonadotrophin Secretion ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Dose Response Curves ◽  
Male Rhesus

The effects of bovine inhibin, testosterone and GnRH on gonadotrophin secretion by primate pituitary cells were characterized in vitro using pituitaries from six male rhesus monkeys and one male cynomolgus monkey. The effect of inhibin on basal secretion of FSH and LH was investigated. Dose-response curves in monkeys and rats were compared. GnRH dose-response curves in the presence and absence of testosterone were also examined in monkeys. In monkey pituitary cells, testosterone at a concentration of 10(-7) M had no effect on LH or FSH secretion. Inhibin suppressed FSH secretion to 50.8% of that of controls with no effect on LH. In rats, FSH secretion was suppressed to 45.0% of that of controls with a median effective dose (ED50, 95% range) of 1.298 (1.064-1.584) U/ml, compared with 1.024 (0.7204-1.455) U/ml in monkeys. In monkey pituitary cells, LH release was stimulated 9.9-fold and FSH 3.3-fold by GnRH. Testosterone had no effect on basal or GnRH-stimulated gonadotrophin release. These results support the view that the pituitary is not the target organ for the negative feedback action of testosterone in the male. In vitro, inhibin is the major regulator of FSH secretion at the pituitary level.

Gonadotrophin-releasing activity of neurohypophysial hormones: II. The pituitary oxytocin receptor mediating gonadotrophin release differs from that of corticotrophs

1989 ◽  
Vol 122 (1) ◽  
pp. 107-116 ◽  
Author(s):  
J. J. Evans ◽  
K. J. Catt
Keyword(s):  
Calcium Concentration ◽  
Phosphodiesterase Inhibitor ◽  
Pituitary Cells ◽  
Neurohypophysial Hormones ◽  
Gonadotrophin Secretion ◽  
Agonist And Antagonist ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Type Receptor

ABSTRACT Neurohypophysial hormones stimulate gonadotrophin release from dispersed rat anterior pituitary cells in vitro, acting through receptors distinct from those which mediate the secretory response to gonadotrophin-releasing hormone (GnRH). The LH response to oxytocin was not affected by the presence of the phosphodiesterase inhibitor, methyl isobutylxanthine, but was diminished in the absence of extracellular calcium and was progressively increased as the calcium concentration in the medium was raised to normal. In addition, the calcium channel antagonist, nifedipine, suppressed oxytocin-stimulated secretion of LH. It is likely that the mechanisms of LH release induced by GnRH and neurohypophysial hormones are similar, although stimulation of gonadotrophin secretion is mediated by separate receptor systems. Oxytocin was more active than vasopressin in releasing LH, but less active in releasing ACTH. The highly selective oxytocin agonist, [Thr4,Gly7]oxytocin, elicited concentration-dependent secretion of LH but had little effect on corticotrophin secretion. The neurohypophysial hormone antagonist analogues, [d(CH2)5Tyr(Me)2]-vasopressin, [d(CH2)5Tyr(Me)2,Orn8]vasotocin and [d(CH2)5d-Tyr(Et)2Val4,Cit8]vasopressin, inhibited the LH response to both oxytocin and vasopressin. However, [d(CH2)5Tyr(Me)2]vasopressin was much less effective in inhibiting the ACTH response to the neurohypophysial hormones, and [d(CH2)5Tyr-(Me)2,Orn8]vasotocin and [d(CH2)5d-Tyr(Et)2,Val4, Cit8]vasopressin exhibited no inhibitory activity against ACTH release. Thus, agonist and antagonist analogues of neurophypophysial hormones display divergent activities with regard to LH and ACTH responses, and the neuropeptide receptor mediating gonadotroph activation is clearly different from that on the corticotroph. Whereas the corticotroph receptor is a vasopressin-type receptor an oxytocin-type receptor is responsible for gonadotrophin release by neurohypophysial hormones. Journal of Endocrinology (1989) 122, 107–116

Biphasic modulation of pituitary sensitivity to GnRH by oestrogens: the effects of A- and D-ring substitution on LH release in cultured pituitary cells

1984 ◽  
Vol 107 (3) ◽  
pp. 317-327 ◽  
Author(s):  
G. Emons ◽  
R. Knuppen ◽  
P. Ball ◽  
K.J. Catt
Keyword(s):  
Dose Response ◽  
High Sensitivity ◽  
Female Rats ◽  
Pituitary Cells ◽  
Response Curves ◽  
Methyl Group ◽  
Lh Release ◽  
Dose Response Curves ◽  
Sensitizing Effect ◽  
Almost All

Abstract. The sensitizing effect of oestrogens on GnRH-stimulated LH release was evaluated in pituitary cells from adult female rats, cultured for 2 days in the presence of 10−13 to 10−6 m concentrations of oestradiol and selected A- and D-ring modified oestrogens. With almost all steroids tested, bell-shaped dose-response curves with comparable LH-maxima but different EDmax values were obtained for the LH response to a submaximal GnRH stimulus (5 × 10−10 m). Maximal LH response to 5 × 10−10 m GnRH were found at the following oestrogen concentrations: oestradiol and 4-hydroxyoestradiol = 10−11 m; 2-methyloestradiol = 10−9 m; 2-hydroxyoestradiol = 10−8 m; with 4-methyloestradiol no significant maximum was observed. When cells were pretreated with 10−13, 10−11 and 10−9 m oestradiol, or 4-hydroxyoestradiol, or 2-hydroxyoestradiol, and exposed to increasing concentrations of GnRH (10−11 to 10−7 m), an almost 10-fold decrease in the ED50 for GnRH was observed after pretreatment with 10−11 m oestradiol and 4-hydroxyoestradiol. With 2-hydroxyoestradiol at this concentration, the sensitizing effect was much less pronounced. Increasing the steroid concentration to 10−9 m slightly decreased the effect of oestradiol and 4-hydroxyoestradiol, whereas it increased the effect of 2-hydroxyoestradiol. Thus, at the target cell 4-hydroxyoestradiol has the same potency as oestradiol, while 2-hydroxyoestradiol is significantly less active. The sensitizing effect of oestradiol is only slightly decreased by the presence of a methyl group in position 2, but is markedly reduced by a methyl group in position 4. Our results also demonstrate the high sensitivity of the pituitary to oestrogen-induced enhancement of GnRH-stimulated gonadotrophin release, as well as the decrease of the positive effect at high oestrogen concentrations. The bell-shaped dose-response curves for oestrogen action should be taken into account when evaluating the effects of oestrogens and their derivatives upon gonadotrophin release from the pituitary gland.

Varying the patterns and concentrations of gonadotrophin-releasing hormone stimulation does not alter the ratio of LH and FSH released from perifused sheep pituitary cells

1986 ◽  
Vol 109 (2) ◽  
pp. 155-161 ◽  
Author(s):  
J. E. A. McIntosh ◽  
R. P. McIntosh
Keyword(s):  
Dose Response ◽  
Dose Interval ◽  
Follicular Phase ◽  
Pituitary Cells ◽  
Ovulatory Cycle ◽  
Short Term ◽  
Releasing Hormone ◽  
Dissociated Cells ◽  
Gonadotrophin Releasing Hormone

ABSTRACT Our aim was to determine whether release of LH and FSH can be controlled differentially by the characteristics of applied signals of stimulatory gonadotrophin-releasing hormone (GnRH) alone, free of the effects of steroid feedback or other influences from the whole animal. The outputs of both gonadotrophins were significantly correlated (r≈0·90; P<0·0005) when samples of freshly dispersed sheep pituitary cells were perifused in columns for 7 h with medium containing a range of concentrations of GnRH in various patterns of pulses. Hormone released in response to the second, third and fourth pulses from every column was analysed in detail. Dose–response relationships for both LH and FSH were very similar when cells were stimulated with 5–8500 pmol GnRH/1 in 5-min pulses every hour. When GnRH was delivered in pulses at a maximally stimulating level, the outputs of both hormones increased similarly with increasing inter-pulse intervals. Efficiency of stimulation (release of gonadotrophin/unit stimulatory GnRH) decreased (was desensitized) with increasing pulse duration in the same way for both hormones. Thus, varying the dose, interval and duration of GnRH pulses did not alter the proportions of LH and FSH released in the short-term from freshly dissociated cells. However, the same cell preparations released more LH relative to FSH when treated with maximally stimulating levels of GnRH for 3 h in the presence of 10% serum from a sheep in the follicular phase of its ovulatory cycle compared with charcoal-treated serum. Because there was no gonadotrophin synthesis under the conditions used in vitro these results suggest that changes in the LH/FSH ratio seen in whole animals are more likely to result from differential clearance from the circulation, ovarian feedback at the pituitary, differential synthesis in intact tissue or another hormone influencing FSH secretion, rather than from differences in the mechanism of acute release controlled by GnRH. J. Endocr. (1986) 109, 155–161

scholarly journals Physiologically based kinetic modelling based prediction of in vivo rat and human acetylcholinesterase (AChE) inhibition upon exposure to diazinon

2021 ◽  
Author(s):  
Shensheng Zhao ◽  
Sebastiaan Wesseling ◽  
Bert Spenkelink ◽  
Ivonne M. C. M. Rietjens
Keyword(s):  
Dose Response ◽  
Kinetic Modelling ◽  
Ache Inhibition ◽  
Response Curves ◽  
Alternative Testing ◽  
Dose Response Curves ◽  
Physiologically Based Kinetic Modelling ◽  
Point Of Departure

AbstractThe present study predicts in vivo human and rat red blood cell (RBC) acetylcholinesterase (AChE) inhibition upon diazinon (DZN) exposure using physiological based kinetic (PBK) modelling-facilitated reverse dosimetry. Due to the fact that both DZN and its oxon metabolite diazoxon (DZO) can inhibit AChE, a toxic equivalency factor (TEF) was included in the PBK model to combine the effect of DZN and DZO when predicting in vivo AChE inhibition. The PBK models were defined based on kinetic constants derived from in vitro incubations with liver fractions or plasma of rat and human, and were used to translate in vitro concentration–response curves for AChE inhibition obtained in the current study to predicted in vivo dose–response curves. The predicted dose–response curves for rat matched available in vivo data on AChE inhibition, and the benchmark dose lower confidence limits for 10% inhibition (BMDL10 values) were in line with the reported BMDL10 values. Humans were predicted to be 6-fold more sensitive than rats in terms of AChE inhibition, mainly because of inter-species differences in toxicokinetics. It is concluded that the TEF-coded DZN PBK model combined with quantitative in vitro to in vivo extrapolation (QIVIVE) provides an adequate approach to predict RBC AChE inhibition upon acute oral DZN exposure, and can provide an alternative testing strategy for derivation of a point of departure (POD) in risk assessment.

scholarly journals Modelling the population-level protection conferred by COVID-19 vaccination

2021 ◽  
Author(s):  
Pranesh Padmanabhan ◽  
Rajat Desikan ◽  
Narendra M Dixit
Keyword(s):  
Mathematical Model ◽  
Severe Acute Respiratory Syndrome ◽  
Dose Response ◽  
Neutralizing Antibodies ◽  
Population Level ◽  
Response Curves ◽  
Post Vaccination ◽  
Dose Response Curves ◽  
Vaccine Availability

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines work predominantly by eliciting neutralizing antibodies (NAbs), how the protection they confer depends on the NAb response to vaccination is unclear. Here, we collated and analysed in vitro dose-response curves of >70 NAbs and constructed a landscape defining the spectrum of neutralization efficiencies of NAbs elicited. We mimicked responses of individuals by sampling NAb subsets of known sizes from the landscape and found that they recapitulated responses of convalescent patients. Combining individual responses with a mathematical model of within-host SARS-CoV-2 infection post-vaccination, we predicted how the population-level protection conferred would increase with the NAb response to vaccination. Our predictions captured the outcomes of vaccination trials. Our formalism may help optimize vaccination protocols, given limited vaccine availability.

Histamine H2-receptor of human and rabbit parietal cells

1987 ◽  
Vol 253 (4) ◽  
pp. G497-G501 ◽  
Author(s):  
R. Leth ◽  
B. Elander ◽  
U. Haglund ◽  
L. Olbe ◽  
E. Fellenius
Keyword(s):  
Dose Response ◽  
In Vivo Model ◽  
Response Curves ◽  
Gastric Glands ◽  
Histamine H2 Receptor ◽  
Receptor Affinity ◽  
H2 Receptor ◽  
Dose Response Curves

The histamine H2-receptor on the human parietal cell has been characterized by using dose-response curves and the negative logarithm of the molar concentration of an antagonist (pA2) analyses of cimetidine antagonism of betazole, histamine, and impromidine stimulation in isolated human and rabbit gastric glands. To evaluate the in vitro results, betazole-stimulated gastric acid secretion with and without cimetidine was also studied in healthy subjects. In the in vivo model, individual dose-response curves were shifted to the right with increasing cimetidine concentrations, but this was counteracted by increasing betazole doses, indicating competitive, reversible antagonism. The pA2 values ranged from 6.1 to 6.3. In isolated human gastric glands, impromidine was shown to be eight times more potent than histamine, indicating higher receptor affinity, but the maximally stimulated aminopyrine accumulation was the same as for histamine, and the pA2 values for cimetidine antagonism did not differ significantly, i.e., 5.7 (histamine) and 6.1 (impromidine). In isolated rabbit gastric glands, cimetidine inhibited the histamine- and impromidine-stimulated response with pA2 values of 6.0 and 7.3, respectively. Impromidine was shown to be approximately 100 times more potent than in human gastric glands, whereas histamine had the same potency. This confirms the role of the histamine H2-receptor and suggests a difference between the species concerning receptor affinity.

AN IN VITRO ASSAY OF CORTICOTROPHIN

1955 ◽  
Vol 33 (2) ◽  
pp. 209-216 ◽  
Author(s):  
K. W. McKerns ◽  
E. Nordstrand
Keyword(s):  
Dose Response ◽  
In Vitro Assay ◽  
Assay Method ◽  
Response Curves ◽  
Vitro Assay ◽  
Rat Adrenals ◽  
Assay Design ◽  
Dose Response Curves ◽  
Gland System

The ability of corticotrophin to increase the corticoid output of rat adrenals in an isolated gland system has been developed as a useful assay method for the measurement of corticotrophin potency. The extra corticoids produced by stimulation are measured in terms of cortisone. Log dose response curves are presented for corticotrophin levels from 0.002 to 0.135 I.U./100 mgm. adrenals. A four point assay design, the precision of corticoid measurements, and the characteristics of the log dose response curves for a number of types of corticotrophin are given. With four measurements of each dose level the average lambda s/b for 20 assays was 0.209 ± 0.085 (S.D.).

AN IN VITRO ASSAY OF CORTICOTROPHIN

1955 ◽  
Vol 33 (1) ◽  
pp. 209-216
Author(s):  
K. W. McKerns ◽  
E. Nordstrand
Keyword(s):  
Dose Response ◽  
In Vitro Assay ◽  
Assay Method ◽  
Response Curves ◽  
Vitro Assay ◽  
Rat Adrenals ◽  
Assay Design ◽  
Dose Response Curves ◽  
Gland System

The ability of corticotrophin to increase the corticoid output of rat adrenals in an isolated gland system has been developed as a useful assay method for the measurement of corticotrophin potency. The extra corticoids produced by stimulation are measured in terms of cortisone. Log dose response curves are presented for corticotrophin levels from 0.002 to 0.135 I.U./100 mgm. adrenals. A four point assay design, the precision of corticoid measurements, and the characteristics of the log dose response curves for a number of types of corticotrophin are given. With four measurements of each dose level the average lambda s/b for 20 assays was 0.209 ± 0.085 (S.D.).

BIOLOGICALLY ACTIVE LUTEINIZING HORMONE (LH) IN PLASMA

1976 ◽  
Vol 83 (3) ◽  
pp. 454-465 ◽  
Author(s):  
P. Romaní ◽  
D. M. Robertson ◽  
E. Diczfalusy
Keyword(s):  
Menstrual Cycle ◽  
Dose Response ◽  
Gel Filtration ◽  
Biologically Active ◽  
Relative Potency ◽  
Response Curves ◽  
Plasma Pool ◽  
Dose Response Curves ◽  
Post Menopausal

ABSTRACT A recently described in vitro bioassay method for the measurement of biologically active LH (Van Damme et al. 1974) has been applied to the plasma of normally menstruating and post-menopausal women. The specificity of the procedure was established according to the following evidence: 1. Parallelism was observed between dose response curves obtained with serial dilutions of a standard LH preparation (HMG 2nd IRP) and plasma pools collected during the follicular phase, at the LH-peak, during the luteal phase and after menopause. 2. There was no evidence for the presence of any synergistic or antagonistic factor in the various plasma specimens. The assay design used to establish this consisted of assaying the standard and plasma pool separately and then together as a mixture followed by an asssessment of the difference (if any) in the potencies obtained. Strict additivity should yield a relative potency of 1.0. Plasma pools which were obtained every 2–3 days throughout the menstrual cycle were assayed using this design against the standard (HMG 2nd IRP) and against a mid-cycle plasma pool obtained at the time of the LH-peak. The latter was also assayed against partially purified plasma fractions obtained from a post-menopausal plasma pool after gel filtration and isoelectric focusing. With the exception of 3 assays, in which the estimates of relative potency were 0.91, 0.94 and 0.95, respectively, in 19 assays of additivity, the fiducial limits always included unity. 3. Non-detectable LH levels were found in the plasma or serum of either hypophysectomized or hypopituitary hypogonadal men or women treated with oestrogen/progestogen combined pills. 4. The presence of calf or human serum in the assay medium is an essential requirement for a valid comparison of standard and unknown preparations. In their absence, non-parallel dose response curves between plasma and standard were obtained. The other established criteria of reliability (sensitivity and precision) were also examined. The method is sufficiently sensitive (3.5–8.0 mIU/ml plasma; HMG (2nd IRP) as standard) for the measurement of LH throughout the cycle. The mean index of precision (λ) in 230 multiple assays was 0.040. It is concluded that the modified bioassay yields valid and reliable estimates of LH when applied to human plasma obtained throughout the menstrual cycle and after menopause.

Differential response of primary cultures of breast carcinomas to lapatinib in an in vitro chemoresponse assay

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 1115-1115
Author(s):  
L. M. Hancher ◽  
P. R. Ervin ◽  
S. L. Brower
Keyword(s):  
Cell Lines ◽  
Dose Response ◽  
Response Rate ◽  
Primary Cultures ◽  
Breast Carcinomas ◽  
Human Breast ◽  
Response Curves ◽  
Her 2 ◽  
Dose Response Curves

1115 Background: Lapatinib (Tykerb) is a small molecule tyrosine kinase inhibitor that targets the intracellular domain of the epidermal growth factor receptor and HER-2, thereby inhibiting both growth and survival signaling pathways. Lapatinib is currently FDA-approved to treat HER-2-positive breast cancer previously treated with anthracycline and taxane therapies and trastuzumab. Due to the low population response rate of lapatinib, an integrated biomarker that can identify patients with an increased likelihood for response would be of great clinical utility. The current study describes an in vitro chemoresponse assay developed to predict sensitivity and resistance of primary cultures of human breast tumor specimens to lapatinib. Methods: The chemoresponse assay (ChemoFx) for lapatinib was developed using four different immortalized carcinoma cell lines (SK-OV3, BT474, MDA-MB-231, MCF7). In addition to cell lines, the chemoresponse assay was also performed on 55 first passage primary cultures of human breast carcinomas. All cultures were confirmed to contain keratin-positive epithelial cells using fluorescence immunocytochemistry. Cell lines and specimens were treated with a 10 dose concentration range of lapatinib for 72 hours and stained with DAPI; remaining live cells were counted on an inverted fluorescent imaging system. Resulting dose-response curves were analyzed and categorized as responsive, intermediate responsive, or non-responsive using a proprietary scoring algorithm. Results: All four cell lines (BT474, MDA-MB-231, MCF7, SK-OV3) were responsive to lapatinib treatment, with EC50 values of approximately 10 uM. Dose-response curves of the 55 primary breast cultures revealed that 9% of the specimens tested were responsive to lapatinib, 15% had an intermediate response, and 76% were non-responsive. These results are consistent with a reported clinical response rate of 10% for lapatinib. Conclusions: Initial results with the described integrated cell-based assay demonstrate that in vitro chemoresponse testing may be useful in predicting patient response to lapatinib. This type of in vitro biomarker is likely to increase the efficacy of the current chemotherapy decision-making process for oncologists and their patients. No significant financial relationships to disclose.

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