Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The secretory response of pituitary gonadotropes to stimulation by gonadotropin-releasing hormone (GnRH) has been extensively studied, but the mechanism by which GnRH evokes gonadotropin synthesis and release has not been clarified. In particular, there has been conflicting evidence about the role of cAMP in GnRH-induced release of LH. To examine this question in more detail, the actions of GnRH on LH release and cAMP production were analyzed in primary cultures of collagenase-dispersed rat pituitary cells. In this system, addition of 10(-10)--10(-6) M GnRh to cultured pituicytes caused rapid release of LH into the incubation medium. In contrast, GnRH caused no significant change in intracellular or extracellular cAMP or in occupancy by cAMP of the regulatory subunit of protein kinse. Neither dibutyryl cAMP nor methyl isobutylxanthine (MIC) stimulated LH production to the same level as GnRH, and neither agent potentiated the effect of the releasing hormone. Cholera toxin and prostaglandin E1 (PGE1), both of which stimulated cAMP production in cultured pituicytes, did not raise LH levels as markedly as GnRH. These results demonstrate the independence of LH release from cAMP accumulation in cultured pituicytes, suggesting that cAMP is not required for stimulation of LH release from these cells and that GnRH acts on LH secretion by a different mechanism.
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PMID:Gonadotropin-releasing hormone action in cultured pituicytes: independence of luteinizing hormone release and adenosine 3',5'-monophosphate production. 22 Nov 78

An in vitro system consisting of the rat hypothalamic tissue, the collagenase-digested isolated anterior pituitary cells and the Leydig cells, has been employed, where the testosterone production of the incubated Leydig cells was measured as the end point. The method appeared to be highly sensitive and specific in studying the functional interrelations of hypothalamus-pituitary-testis system. The sensitivity of the Leydig cells to hCG was 0.1--1.0 mU per 10(6) cells, and that of the anterior pituitary cells to LHRH responding with LH release was in the range of 0.1--1.0 ng per 10(6) cells. Two hypothalamic blocks can release a sufficient amount of LHRH to produce LH secretion in the pituitary cell preparation. The described technique seems to be a suitable in vitro approach for measuring the functional activity of the system studied and for evaluation of the sites of response to various external agents.
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PMID:Technique for study of hypothalamus (-) pituitary (-) testis function in vitro. 39 2

The effect of prostaglandins (PG) A1, E1, E2 and F2 alpha in the concentration range of 10(-7)--10(-4) M were studied in vitro on a rat hypothalamic tissue, collagenase-digested isolated anterior pituitary cell and Leydig cell suspension system by measuring the testosterone production of incubated Leydig cells. PGs did not change the testosterone production and the hCG sensitivity of the Leydig cells, nor the LH secretion and the LHRH sensitivity of the anterior pituitary cells. PGE2 at concentrations of 10(-6), 10(-5) and 10(-4) M significantly increased the hypothalamic tissue-induced pituitary-testicular activation, and this stimulatory effect of PGE2 was dose dependent. PGA1, PGE1 and PGF2 alpha did not alter hypothalamic LHRH release measured in vitro. The results suggest that PGE2 has a direct stimulatory effect on hypothalamic LHRH release.
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PMID:Effect of prostaglandins on hypothalamic-pituitary-testicular function in vitro. 39 65

In the present study, the method of collagenase-pepsin prepared cell suspension of human placental villi from early (10-12 weeks) and term (38-40 weeks) gestation cultured in vitro combined with progesterone radioimmunoassay was employed. The results indicated that: 1. In the placenta villi cells from early and term gestation in vitro, both exogenous and endogenous hCG showed a stimulatory effect on progesterone secretion, and the effect was approximately proportional to the concentration of the exogenous hCG added. 2. In the placenta villi cells from term gestation in vitro, after addition of sufficient rabbit antihCG IgG to the culture medium, LHRH-A exhibited no obvious influence on this hCG-independent progesterone secretion. However, in the absence of rabbit anti-hCG IgG in the culture medium, LHRH-A showed a stimulatory action on progesterone secretion probably via its stimulatory effect on hCG secretion which could subsequently increase the progesterone secretion. 3. In the placenta villi cells from early gestation, LHRH-A exhibited an inhibitory effect on both hCG-independent and hCG-dependent progesterone secretion.
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PMID:[The effects of HCG and LHRH-A on progesterone secretion by human placenta villi cells of early and term gestation in vitro]. 228 76

This study investigated the direct effect of catecholamines, epinephrine (EPI), and norepinephrine (NE) on basal and gonadotropin-releasing hormone (GnRH)-stimulated secretion of luteinizing hormone (LH) from dispersed pig pituitary cells in vitro. Pig pituitaries were dispersed into cells with collagenase and DNAase and then cultured in McCoy's 5a medium containing horse serum (10%) and fetal calf serum (2.5%) pretreated with dextran-coated charcoal for 3 days. EPI and NE did not affect basal LH secretion after 4 h of incubation. When pituitary cells were incubated with EPI or NE (1 microgram/ml) for longer than 30 min, GnRH-stimulated LH secretion was reduced. The degree of this reduction was dependent on EPI and NE, and a concentration of EPI and NE higher than 1 ng/ml and 100 ng/ml, respectively, was needed. L-isoproterenol, a nonselective beta-agonist, also inhibited the LH response to GnRH. Propranolol, a beta-antagonist, blocked the inhibitory effect of EPI, whereas phentolamine, an alpha-antagonist, had no effect. These results suggest that catecholamines, acting by a beta 2-adrenergic receptor, may play a role in the control of the porcine pituitary gonadotrope's response to GnRH.
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PMID:Catecholamine inhibition of luteinizing hormone secretion in isolated pig pituitary cells. 266 85

The effect of cortisol or adrenocorticotropic hormone (ACTH) on basal and gonadotropin-releasing hormone (GnRH)-induced secretion of luteinizing hormone (LH) was studied in vitro using dispersed pig pituitary cells. Pig pituitary cells were dispersed with collagenase and DNAase and then grown in McCoy's 5a medium containing 10% dextran charcoal-pretreated horse serum and 2.5% fetal calf serum for 3 days. Cells were preincubated with cortisol or ACTH before GnRH was added. When pituitary cells were incubated with 400 micrograms cortisol/ml medium for 6 h or longer, increase basal secretion of LH was observed. However, GnRH-induced LH release was reduced by cortisol. The degree of this reduction was dependent on cortisol, and a concentration of cortisol higher than 100 micrograms/ml was needed. Cortisol also inhibited the 17 beta-estradiol-induced increase in GnRH response. ACTH-(1-24), ACTH-(1-39), or porcine ACTH had no influence on GnRH-induced LH secretion. Our results show that cortisol can act directly on pig pituitary to inhibit both normal and estradiol-sensitized LH responsiveness to GnRH.
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PMID:Effect of cortisol or adrenocorticotropic hormone on luteinizing hormone secretion by pig pituitary cells in vitro. 282 56

The characteristics of the steroidogenic response of reaggregated rat interstitial cells were examined in a perifusion system. Interstitial cells were isolated from 19-day-old rat testes by digestion with collagenase. The cells were cultured for 3 days as monolayers and were resuspended by brief treatment with trypsin. Constant gyratory shaking of the dispersed cells resulted in the formation of round and compact aggregates of 70-140 microns. The functional characteristics of these aggregates were examined by studying the output of cAMP, C19 steroids (testosterone and androstenedione), and C21 steroids (progesterone, 17 alpha-hydroxyprogesterone, 20 alpha-hydroxypregn-4-en-3-one) in a perfusion system. It is demonstrated that reaggregated interstitial cells maintain their responsiveness to LH, LHRH, and Leydig cell stimulatory factor(s) produced by Sertoli cells for at least 12 days. When exposed to low concentrations of LH (1 ng/ml), either in a continuous or in a pulsatile fashion, perifused aggregates maintain a constant output of steroids for more than 20 h. Under these conditions, LH-dependent differentiation of the steroidogenic machinery can be observed in vitro. In fact, although the sum of the measured steroids remains constant, C21 steroids progressively decrease whereas C19 steroid output increases during perifusion. When perifused with high concentrations of LH (10 ng/ml), desensitization becomes the predominant phenomenon. It is demonstrated that the steroid output of reaggregated interstitial cells considerably exceeds that of similarly treated cells maintained as monolayers. Moreover, perifusion of aggregates results in a 6-fold increase in steroid output as compared to static incubation and in a selective increase in androgen output. It is concluded that prepubertal interstitial cells allowed to reaggregate in suspension culture form functional multicellular structures. Perifusion of these aggregates is a useful tool in the study of the dynamics of the regulation of steroidogenesis.
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PMID:The dynamics of steroid and adenosine 3',5'-cyclic monophosphate output in perifused interstitial cell aggregates derived from prepubertal rat testes. 301 35

A superfusion method consisting of fully recovered, dissociated pituitary cells adhering to Cytodex beads has proved useful in monitoring the dynamics of hormone secretion over time. Male rat anterior pituitaries were dissociated with collagenase and Viokase, then cultured in the presence of Cytodex beads for 3-5 days, during which time the cells attached firmly to the surface of the beads. The bead-attached cells were stable and could be transferred to any vessel without the need for centrifugation or further trypsinization. For this application, the bead-attached cells were packed in a column and superfused with a low bicarbonate buffer requiring no CO2 gassing. Viability was more than 95% after 48 h in the column. The cells responded in a normal physiological manner to hypothalamic releasing and inhibitory peptides. The ED50 was 0.3 nM for somatostatin and 1.2 nM for gonadotropin-releasing hormone. A postinhibitory rebound of GH secretion was observed after the discontinuation of large doses of somatostatin. LH secretion reached maximal levels within 6 min after 10 nM gonadotropin-releasing hormone, but started declining after 2 h of continuous stimulation and dropped close to baseline within 18 h. GH release was significantly increased by prostaglandin E2, 3-isobutyl-1-methylxanthine, and 8-bromo-cAMP. LH secretion increased 5-fold in response to 1 mM 8-bromo-cAMP, but showed little increase during prostaglandin E2 or 3-isobutyl-1-methylxanthine stimulation. The cocarcinogen phorbol myristate acetate (12-O-tetradecanoyl-phorbol-13-acetate) induced secretion of all pituitary hormones and continued to do so for hours after a short pulse. The superfusion system is simple to operate and has proven effective in studying transient phenomena, desensitization, and short term kinetics of secretagogues.
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PMID:Superfusion of rat anterior pituitary cells attached to Cytodex beads: validation of a technique. 615 98

Short-term (4 h) incubation of collagenase-dispersed Leydig cells from adult rats in the presence of an LHRH agonist caused a 2-3-fold stimulation (P less than 0.001) of testosterone production. This effect was dose-dependent and as little as 5 x 10(-11) M LHRH agonist caused significant stimulation whilst maximal effects were achieved with 10(-9) M concentrations. Stimulation of steroidogenesis by LHRH agonist was prevented by addition of an antiserum specific for the peptide, but was exaggerated in the presence of the phosphodiesterase inhibitor MIX, suggesting the involvement of cyclic AMP in the response of the Leydig cells to the agonist. Native LHRH caused a similar degree of stimulation of testosterone secretion to LHRH agonist but concentrations 1000 times greater than those of the agonist were required to achieve this, a finding consistent with the known affinities of these 2 peptides for the Leydig cell LHRH-receptor. The addition of LHRH agonist also enhanced (P less than 0.001) testosterone secretion by adult rat Leydig cells in response to hCG or dibutyryl cyclic AMP, and this effect was still evident in the presence of maximally-stimulating concentrations of these factors. LHRH agonist also stimulated testosterone secretion by Leydig cells from immature rats, but this effect differed from that in the adult in being of smaller magnitude and being restricted to effects on basal secretion or secretion elicited by low concentrations of hCG. These results show for the first time (a) that LHRH and its agonists can exert effects on Leydig cell steroidogenesis during short-term incubation, and (b) that these effects are stimulatory, which contrasts with the inhibitory effects reported after long-term (2-3 days) exposure of Leydig cells to LHRH agonists in vivo and in vitro. The availability of this simple and rapid measure of a biological action of LHRH on the Leydig cell should enable its precise mode of action to be determined, and should throw light on the physiological role of endogenously produced testicular 'LHRH'.
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PMID:Stimulatory effect of LHRH and its agonists on Leydig cell steroidogenesis in vitro. 617 69

The properties of gonadotropin-releasing hormone (GnRH) receptors were analyzed in isolated pituitary cells prepared by enzymatic dispersion with trypsin or collagenase-hyaluronidase. The initial impairment of LH responses to GnRH in isolated cells prepared by both methods was reversed during culture for 2 days in multiwell vessels. However, specific binding sites for GnRH, assayed by equilibration with [125I]iodi0[D-Ser(t-BU)6]des-Gly10-GnRH N-ethylamide (GnRH-A) were demonstrable in collagenase-dispersed cells, both initially and after 2 days in culture. Cellular uptake of GnRH-A was temperature dependent, with rapid and saturable binding to a limited number of specific receptor sites with high affinity for the labeled analog (Ka = 4.0 +/- 0.8 X 10(9) M-1). These sites showed common binding specificity for GnRH-A and the native GnRH peptide, with significantly lower affinity for the natural peptide (Ka = 2.3 X 10(7) M-1). Other protein and peptide hormones, including ovine LH, ovine PRL, hCG, TRH, somatostatin, and angiotensin II (up to 10(-6) M) did not inhibit binding of GnRH-A to its receptors. Cellular binding of GnRH-A was followed by increased cGMP production and LH release within 10 min. The analog was 50 times more potent than native GnRH in stimulating LH release. The Kact values derived for GnRH and GnRH-A were 0.5 and 0.01 nM, respectively, considerably lower than the Kd values of 50 and 0.25 nM derived from receptor binding analysis. These results indicate that GnRH receptors can be identified in isolated pituitary cells, in which peptide binding is followed by increased cGMP production and LH release. The impaired LH responses in acutely dispersed pituitary cells are not due to the loss of receptor sites but to a reversible postreceptor defect. Occupancy of about 20% of the GnRH-binding sites elicits a near-maximal LH response, indicating the nonlinearity of GnRH-receptor coupling to secretory responses in the cultured gonadotroph.
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PMID:Characterization of gonadotropin-releasing hormone receptors in cultured rat pituitary cells. 625 Jul 93


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