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

---

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

The in vitro effects of ovine PRL (oPRL) on testicular testosterone synthesis were determined using isolated, collagenase-dispersed, adult rat Leydig cells in culture. oPRL (50-1000 ng/ml) had no effect either on basal or on LH (50, 100 or 2000 pg/ml)-stimulated testosterone secretion by Leydig cells in short-term culture (4 h). 125I-oPRL binding studies revealed a single class of high affinity sites (Ka 8.7 nM) with a low capacity (Bmax 6.7 fmol/mg protein identical to approximately 980 sites/Leydig cell). Isolated Leydig cells were further purified on a continuous Percoll gradient and cultured in serum-free medium, at 34 degrees C, in 5% CO2 and 95% air. After 3 days of culture, the media were collected, the cells washed and then stimulated with hCG (3 ng/ml) for 3 h. oPRL (1-1000 ng/ml) added at plating, caused a log dose-dependent inhibition of testosterone accumulation during the 3-day culture period; the highest and most consistent inhibition (31%) was with 500 ng/ml oPRL. hCG increased the sensitivity to the inhibitory effect of PRL, 10 ng/ml oPRL causing 40% inhibition and 100 ng/ml causing a maximal inhibition of 50%. PRL in fact caused a reduction in the maximal effect (efficacy) of hCG on steroidogenesis, without significantly affecting the ED50 (sensitivity). The effects of an antiPRL receptor antibody raised by the antiidiotypic route and previously shown to bind to rat testis PRL receptors were tested. The antiPRL receptor IgG (13 micrograms/ml) mimicked the PRL inhibitory effect and acted synergistically with PRL (100 ng/ml) in inhibiting both testosterone accumulation in 3-day cultured Leydig cells and their subsequent response to hCG. In summary, a clear inhibitory effect of PRL and a synergistic effect of antiPRL receptor antibody were demonstrated on testosterone synthesis by rat Leydig cells in 3-day culture.
...
PMID:Prolactin and antiprolactin receptor antibody inhibit steroidogenesis by purified rat Leydig cells in culture. 362 21

We investigated the direct effects of bromocriptine (BR) on both basal and hCG-stimulated testosterone production by rat collagenase-dispersed Leydig cells. In a final volume of 2.2 ml, 2.10(6) Leydig cells were incubated at 33 degrees C for 3 h either alone or with various amounts of hCG (1. 10. 10(2). 10(3). 10(4) mUI/vial) and BR (1.5 10(-9), 1.5 10(-7), 1.5 10(-5) M); BR was dissolved in 20 microliters of ethanol. BR (1.5 10(-5) M) decreased significantly both basal and hCG-stimulated testosterone production whereas at lower doses, BR had no effect. These results suggest that the dopamine itself may regulate rat Leydig cell function and that there is room for criticism of BR-induced hypoprolactinemia as an experimental model to study the effect of prolactin on the androgenic function.
...
PMID:Bromocriptine, a dopamine agonist, directly inhibits testosterone production by rat Leydig cells. 400 69

The interaction of seminiferous tubules and Leydig cells was investigated in the rat in vitro. Crude collagenase-dispersed, or Percoll-purified, Leydig cells were incubated together with seminiferous tubules at different stages of the cycle, isolated by transillumination-assisted microdissection. The testosterone production was measured. Seminiferous tubules inhibited testosterone production of crude Leydig cell preparations, but induced a clear stimulation (30-100%) in Percoll-purified cells. The stimulation was maximal at stages VII and VIII of the cycle, significantly higher than at stages II-VI (P less than 0.05). The stimulation by seminiferous tubules was observed both in basal and hCG-stimulated testosterone production. The effect was independent of FSH or GnRH action. These results demonstrate the presence of paracrine regulatory interaction between seminiferous tubules and Leydig cells, and are in agreement with the concept of a preferential androgen requirement of stages VII and VIII of the cycle.
...
PMID:Influence of rat seminiferous tubules on Leydig cell testosterone production in vitro. 609 86

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'.
...
PMID:Stimulatory effect of LHRH and its agonists on Leydig cell steroidogenesis in vitro. 617 69

The sensitivity to hCG-stimulation in vitro of intact hemi-testes and collagenase-dispersed Leydig cells has been compared directly following either an hCG-induced loss of LH-receptors or after a hyperprolactinaemia-induced increase in LH-receptors. Injection of hCG 65 h previously, reduced hCG-binding to dispersed Leydig cells by over 84%. The sensitivity of the steroidogenic response of these cells to hCG-stimulation in vitro was reduced 22-fold whereas intact testes from the same animals showed only a 3-fold reduction in sensitivity to hCG. Dispersed Leydig cells from control rats were 8 times more sensitive to hCG-stimulation than intact testes from the same rats, a difference not evident with hCG-injected rats. In contrast, there was no difference between intact testes and dispersed Leydig cells from control and hCG-injected rats in their sensitivity to stimulation with dibutyryl cyclic AMP in vitro. Induction of hyperprolactinaemia increased hCG-binding to dispersed Leydig cells by 55%. The sensitivity of these cells to hCG-stimulation in vitro was increased by a factor of 4.5, a difference not found with intact testes from the same animals. These results show that experimental manipulation of LH-receptor numbers alters the sensitivity of dispersed Leydig cells, but not of the intact testis, to hCG-stimulation in vitro, a difference which appears to reside at the receptor level. Possible explanations for these findings are discussed together with their implications with respect to the distribution of LH-receptors over the Leydig cell surface.
...
PMID:Differences between dispersed Leydig cells and intact testes in their sensitivity to gonadotrophin-stimulation in vitro after alteration of LH-receptor numbers. 624 26

Decapsulated testes from adult rats were digested with collagenase, and the fraction enriched in germinal and Leydig cells was applied to a 0-4% continuous metrizamide gradient and centrifuged. This leads to separation of a germinal cell fraction and two putative Leydig cell populations that bind human choriogonadotropin, but only one of which responds to the gonadotropin with marked increase in testosterone production. Adenylate cyclase activity was present in these three fractions, and Mn2+ was more effective than Mg2+ as a divalent cation. The adenylate cyclase activity associated with the germinal cell fraction was just marginally stimulated by fluoride and by the non-hydrolyzable GTP analog 5'-guanylimidodiphosphate, while that associated with the Leydig cell populations was stimulated to a greater degree depending upon the type of divalent cation. Only the Leydig cell populations exhibited marked human choriogonadotropin-sensitive stimulation of adenylate cyclase activity in the presence of 5'-guanylimidodiphosphate above that observed with the GTP analog alone. These results suggest the presence of distinct adenylate cyclases in adult rat testis and indicate that both populations of Leydig cells are capable of producing cyclic AMP in response to gonadotropins such as human choriogonadotropin.
...
PMID:Demonstration of distinct forms of testicular adenylate cyclases associated with germinal and Leydig cell fractions. 628 12

Specific receptors and metabolic responses to luteinizing hormone (LH) were analyzed in testicular Leydig cells purified by centrifugation of collagenase-dispersed rat interstitial cells on density gradients of 14-32% Metrizamide. This procedure separated the interstitial cells into an upper, poorly responsive fraction and a lower, more dense population with high LH receptor content and prominent cyclic AMP and testosterone responses of gonadotropic stimulation. The upper layer consisted of morphologically heterogeneous and extensively vacuolated cells, of which relatively few were structurally identifiable as Leydig cells. The lower layer was comprised of almost homogenous Leydig cells when analyzed by electron microscopy and autoradiography, and sedimented as two adjacent bands with similar hormonal responses and densities of 1.085 and 1.105 g/cm3. The lighter and less responsive cell population appeared to result from the presence of damaged cells in the interstitial cell preparation and could be removed during density gradient isolation of the homogeneous and biologically active Leydig cell fraction. The more dense and active Leydig cell population retained hormonal responsiveness during culture for 24 h and showed loss of LH receptors and low concentrations of gonadotropin in vitro. These findings emphasize the importance of appropriate fractionation of rat interstitial cells to isolate the structurally intact and functionally active population of Leydig cells during studies on LH receptors and section in the testis.
...
PMID:Luteinizing hormone receptors and gonadotropic activation of purified rat Leydig cells. 629 6

Rat interstitial cells were fractionated by centrifugal elutriation to facilitate the purification of Leydig cells for analysis of mechanisms of gonadotropin action in vitro. By this procedure, 10(9) collagenase-dispersed interstitial cells from adult rat testes were separated into 12 fractions in about 1 h. Fractions 1-7 (sedimentation velocities, 1.9-12 mm/h.g) comprised 80-85% of the total cells applied, including erythrocytes, lymphocytes, germinal cells, macrophages, endothelial cells, damaged Leydig cells, and contained less than 4% intact Leydig cells. Fractions 8-12 (sedimentation velocities, greater than 12 mm/h.g) comprised 15-20% of the original cells and contained 90-95% intact Leydig cells. Despite their different sedimentation velocities, the Leydig cell-rich fractions were similar in their LH receptor content (mean +/- SD, 36,115 +/- 4,815 sites/cell) and showed similar 5-fold increases above the original cell preparation in testosterone and cAMP responses to hCG. The pooled Leydig cell-rich fractions (8-12) were further resolved on 16-24% Metrizamide gradients into 5 bands. Bands II-V (density range, 1.075-1.110 g/ml) contained pure Leydig cells, and band I (1.048 g/ml) contained pachytene spermatocytes, the contaminating cell type present in the Leydig cell-rich fractions obtained by elutriation. Each of the 4 Leydig cell-rich bands showed similar morphology and functional activity. Essentially similar results were observed using 14-32% Metrizamide gradients. Leydig cells desensitized in vivo by hCG treatment and isolated by elutriation were also resolved by Metrizamide gradients into 4 bands, but showed a redistribution in the gradient, due to the shift of about 50% of the cells originally present in the heaviest bands to lower density fractions. However, in spite of their changes in density, the Leydig cell bands still showed similar degrees of receptor down-regulation and impairment of the steroid responses to hCG in vitro. This study has demonstrated that centrifugal elutriation is a rapid and effective method for obtaining large quantities of purified (greater than 90%) and active Leydig cells. Further resolution of the Leydig cell-rich fractions in Metrizamide gradients has allowed complete Leydig cell purification, which is not achieved by density gradient centrifugation alone. Since less responsive or inactive Leydig cells displayed various degrees of structural damage, such cells should not be considered as a population of physiological significance.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Functional and morphological studies on isolated Leydig cells: purification by centrifugal elutriation and metrizamide fractionation. 631 57

Single Leydig cells were isolated from rat testis by a collagenase digestion procedure and purified through a 21,000 g self generated densities gradient of 35% Percoll. A method including collagen and fibronectin was proposed to attach freshly prepared Leydig cells to the bottom of plastic Petri dishes. Four hours after the isolation of the cells, it was simultaneously possible to determine their membrane potential by a standard electrophysiological technique using intracellular microelectrodes and to judge cellular integrity by direct microscopic observations. In standard Earle's solution, changes of membrane potentials appeared to be biphasic. On 198 impaled cells, 18 +/- 1 S after the impalement was effective, the membrane potential reached a most negative value (MP1) (-37.6 +/- 0.7 mV), followed by a gradual depolarization to a steady state (MP2) (-25.1 +/- 0.6 mV) which remained constant for a few minutes. In standard Earle's solution, the membrane resistance was low or decreasing towards the most negative potential, then it increased towards the steady potential. At this state, the average value of the cell input resistance was 65.9 +/- 6.0 M omega (n = 16). No action potential was observed either in standard Earle's solution or under a depolarizing current state. It was concluded that the electrophysiological characteristics of the Leydig cell are similar to those of fibroblasts and macrophages, three types of cells with the same mesenchymal origin, present in the interstitial tissue of the rat testis. But the resting potential of the Leydig cell is higher and this secreting cell does not elicit hyperpolarizing oscillations at the steady state, under mechanical or electrical stimuli.
...
PMID:Electrophysiological study of single Leydig cells freshly isolated from rat testis. I. Technical approach and recordings of the membrane potential in standard solution. 647 76

The neonatal human Leydig cell undergoes a transient period of activation during the first months of life. The biological significance of this activation is unknown. Furthermore, little is known about the hormonal regulation of this biological process, even though it coincides with an elevation of LH levels in serum. In order to study the function of human prepubertal testicular culture cells, obtained during the neonatal period, a method for maintaining primary culture cells (isolated from testes collected at necropsy) in culture was developed. Within 24 h after death, testes were collected from 1-36-month-old subjects. Subjects were divided into two age groups, based on the presence or absence of fetal Leydig cells: 1-7-month-old infants (group 1) and 12-36-month-old children (group 2). Testes were digested with collagenase, and cells were seeded in multi-well dishes. Cells were grown in serum-free conditioned media supplemented with 5 mg/l vitamin C, 0.2 IU/l vitamin E and 10% fetal bovine serum for 2 days. Cells were then grown for an additional 4 days in serum-free media in the presence or absence of hLH (40 IU/l), hCG (135 IU/l), rh FSH (1.5 IU/l), rhGH (0.12 IU/l) or insulin (0.9 mumol/l). Concentrations of steroids in media were determined by RIA on day 6 of culture. In basal conditions cells of group 1 (n = 11) secreted more testosterone, androstendione, 17-hydroxyprogesterone, progesterone and dehydroepiandrosterone (mean +/- SE: 6.76 +/- 1.86, 7.37 +/- 1.82, 61.9 +/- 1.86, 5.75 +/- 1.74 and 8.51 +/- 3.23 pmol/10(6) cells/24 h, respectively) than cells of group 2 (n = 5) (2.95 +/- 1.15, 1.50 +/- 2.75, 1.44 +/- 2.75, 0.78 +/- 1.74 and 3.23 +/- 1.32, respectively). Under hLH stimulation, cells of group 1 increased testosterone, androstendione and 17-hydroxyprogesterone secretions (to 38.2 +/- 0.89, 13.5 +/- 1.17 and 51.7 +/- 3.23), while progesterone secretion remained unchanged (2.82 +/- 1.20). Cell response to rhFSH and rhGH was similar to that of hLH. On the other hand, medium collected from cultures of cells isolated from a Sertoli cell tumor was able to stimulate testosterone secretion in subcultures of control testicular cells in a way similar to that of hCG. In conclusion, (1) these prepubertal human testicular cells can be maintained in primary culture for several days keeping their in vivo steroidogenic potential; (2) cells isolated from young infants can respond to hLH in culture; (3) response to rhFSH is probably mediated by a paracrine factor; (4) response to rhGH is observed in the absence of gonadotropins.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Human prepubertal testicular cells in culture: steroidogenic capacity, paracrine and hormone control. 762 44


<< Previous 1 2 3 4 5 Next >>

---