Role of calcium and other mediators in aldosterone secretion from the adrenal glomerulosa cells.
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Adrenocorticotropic Hormone↗
Biomedical subjects
J S Davis
Publications and source records attributed to J S Davis.
Mechanisms of hormone action: luteinizing hormone receptors and second-messenger pathways.
The binding of luteinizing hormone/chorionic gonadotropin (LH/CG) to its receptor leads to an orderly cascade of events leading to activation of cytoplasmic effector molecules. The mechanism of action of LH includes stimulation of multiple signal transduction effector systems, including adenylyl cyclase (AC) and inositol phospholipid-specific phospholipase-C (PLC). These effector systems operate by activating families of protein kinases (PKs) which regulate cell metabolism, secretion, gene induction, cellular proliferation and differentiation. The signaling pathways activated by LH interact or cross-talk with the signaling pathways activated by growth factors. The diversity of cellular signaling mechanisms elicited by LH and the potential for interactions with signals generated by growth factors may allow fine tuning of cellular responses during the process of follicular development, ovulation, and corpus luteum formation.
Adenylyl Cyclases↗
Myosin thick filaments and subunit exchange: a stochastic simulation based on the kinetics of assembly.
Subunit exchange between groups of myosin filaments at equilibrium in a volume similar to a sarcomere is simulated using Monte Carlo (probabilistic) methods. Five published kinetic parameters (three rate constants and two cooperativity parameters) which govern the assembly of thick filaments from purified myosin at pH 8.0 are used for the computations. Filament length distributions equivalent to those measured experimentally in the electron microscope result. Distinctive patterns of exchange emerge because cooperativity in myosin assembly is not confined to nucleation but functions throughout growth. Fluctuations in filament size, first apparent in the millisecond time domain, mediate exchange which first occurs at the tips of the filaments and then gradually progresses inwards toward the central bare-zone. Exchange rates decreased by an approximate factor of 10 per decade of time: full exchange takes years, 50% takes 28 h, and 10% takes a brief 100 ms. These data represent the fastest possible rates of exchange because synthetic myosin filaments lack the overall stabilizing influence of the copolymerizing proteins of native filaments. Exchange at equilibrium is therefore too slow to explain, for example, the much faster rates recorded in vivo for the complete replacement of one myosin isoform by another. Facilitated exchange where partial or complete filament dissociation is followed by the introduction of new subunits during reassembly offers a means of accelerating exchange. In this context, it is shown that the requisite disassembly and reassembly of myosin thick filaments can be completed in a minimum of a few seconds.
Animals↗
Kinetic and physical characterization of force generation in muscle: a laser temperature-jump and length-jump study on activated and contracting rigor fibers.
Experiments are presented that probe the mechanism of contraction in normal activated muscle fibers and in heated rigor fibers. In activated fibers we subdivide the partial recovery of isometric tension during the Huxley-Simmons phase 2 into temperature-independent and temperature-dependent steps termed, respectively, phase 2fast and phase 2slow. Evidence is presented to show that phase 2fast arises from the perturbation of a damped elastic element in the cross-bridge and that phase 2slow is the manifestation of an endothermic, order-disorder transition responsible for de novo tension generation. These responses are common to both frog and rabbit fibers. The only difference between animals is that the kinetics of phase 2slow appears to scale with the working temperature of the muscle and not absolute temperature. Rigor fibers heated above the working temperature of the muscle contract. Tension generation is, as with activated fibers, endothermic. Tension transients following a laser temperature-jump of activated and heated rigor fibers are virtually indistinguishable on the basis of either the form or magnitude of the response. In length-jump experiments, tension recovery by heated rigor fibers consists of three exponentials with a tension-dependent rate for the medium speed step. Preliminary data indicate that the rigor cross-bridge operates over a distance of between 13.5 and 18 nm. Collectively, these data imply that tension generation in muscle arises from accessible conformational states in the proteins of the cross-bridge alone. ATP hydrolysis in active fibers and the heating of rigor fibers simply serve to shift these intrinsic conformational equilibria towards tension generation.
Animals↗
The secretion of transforming growth factor-beta by bovine luteal cells in vitro.
Transforming growth factor-beta (TGF-beta), a multifunctional polypeptide growth factor, is produced by follicular cells in the ovary. However, there is little information indicating that TGF-beta is produced in the post-ovulatory follicle, i.e. the corpus luteum. In the present communication we present evidence that bovine luteal cells secrete large amounts of TGF-beta when maintained in moderate-term monolayer culture. Using TGF-beta 1 and TGF-beta 2 subtype-specific antibodies to neutralize the bioactivity it was found that 80-90% TGF-beta activity in luteal cell conditioned medium (LCCM) is due to TGF-beta 1, whereas < or = 10% TGF-beta activity in LCCM is due to TGF-beta 2. TGF-beta subtype nonspecific antibodies effectively and completely neutralized all TGF-beta activity in LCCM. The ratio of TGF-beta 1:TGF-beta 2 as estimated on the basis of neutralization studies was supported by visual observation of TGF-beta 1 and TGF-beta 2 protein bands on Western blotting. Using a modified and rapid mink lung epithelial cell bioassay and authentic TGF-beta to generate standard curves, the amount of TGF-beta secreted by luteal cells in vitro was quantitated. The concentration of luteal cell secreted proteins in the medium increased with time during 7 days of culture. Likewise, the TGF-beta concentration in LCCM increased during 7 days. To study the effect of duration of culture on the rate of TGF-beta secretion by luteal cells, conditioned medium was collected at 24 h intervals and replaced with fresh nutrient medium.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
A single order-disorder transition generates tension during the Huxley-Simmons phase 2 in muscle.
Increasing temperature was used to progressively interconvert non-force-generating into force-generating states in skinned rabbit psoas muscle fibers contracting isometrically. Laser temperature-jump and length-jump experiments were used to characterize tension generation in the time domain of the Huxley-Simmons phase 2. In our experiments, phase 2 is subdivisible into two kinetic steps each with quite different physical properties. The fast kinetic component has rate constant of 950 s-1 at 1 degrees C and a Q10 of approximately 1.2. Its rate is tension insensitive and its normalized amplitude declines with rising temperature--behavior that closely parallels the instantaneous stiffness of the cross-bridge. It is likely that this kinetic step is a manifestation of a damped elastic element/s in the fiber. The slow component of phase 2 is temperature-dependent with a Q10 of approximately 3.0. Its rate is sensitive to tension. Unlike the fast component, its amplitude remains in fixed proportion to isometric tension at different temperatures indicating direct participation in tension generation. Similar T-jump studies on frog fibers are also included. The combined results (frog and rabbit) suggest that tension generation occurs in a single endothermic (entropy driven) step in phase 2.
Animals↗
Characterization of insulin and insulin-like growth factor-I actions in the bovine luteal cell: regulation of receptor tyrosine kinase activity, phosphatidylinositol-3-kinase, and deoxyribonucleic acid synthesis.
The pleiotropic effects of insulin and insulin-like growth factor-I (IGF-I) are mediated via the intrinsic tyrosine kinase activity of their receptors. The potential role of insulin and IGF-I receptor tyrosine kinases in the bovine luteal cell was investigated in terms of autophosphorylation of the receptor and phosphorylation of endogenous and exogenous substrates. Insulin and IGF-I receptors were isolated by wheat germ agglutinin-agarose chromatography and immunoprecipitation with antiphosphotyrosine antibodies (alpha PY20). Insulin and IGF-I treatment of purified receptors or luteal cells in culture resulted in phosphorylation of a protein of 95,000 mol wt. This phosphoprotein was further identified as the autophosphorylated beta-subunit of the insulin/IGF-I receptor by immunoprecipitation with an anti-beta-subunit receptor antibody. The protein tyrosine kinase activity of the receptors was also stimulated after insulin or IGF-I treatment, resulting in a 3- to 4-fold increase in phosphorylation of a synthetic substrate poly(Glu4:Tyr1). Insulin and IGF-I treatment also increased (4.5-fold) phosphatidylinositol-3-kinase (PI-3-kinase) activity in alpha PY20 immunoprecipitates from whole cell lysates, suggesting that this enzyme was regulated by a receptor tyrosine kinase-mediated mechanism. The presence of PI-3-kinase in alpha PY20 immunoprecipitates was further confirmed by the sensitivity of the enzyme to detergents and by immunoblot analysis using a PI-3-kinase antibody. The actions of insulin and IGF-I on tyrosine kinase and PI-3-kinase activity were associated with increased protein and DNA synthesis. Insulin and IGF-I treatment of cultured luteal cells for 18 h increased [3H]thymidine incorporation (6- to 7-fold). The effects of insulin and IGF-I were optimal at 10 micrograms/ml and 50 ng/ml, respectively, and were not additive. The stimulatory effects of insulin and IGF-I on thymidine incorporation were blocked by genistein, a specific inhibitor of protein tyrosine kinase. These findings demonstrate a cascade of insulin and IGF-I receptor tyrosine kinase-mediated pathways in the bovine luteal cell, manifested as increased activity of signal transduction enzymes and increased DNA synthesis.
Animals↗
Greater importance of Ca(2+)-calmodulin in maintenance of ang II- and K(+)-mediated aldosterone secretion: lesser role of protein kinase C.
In this study we have investigated various components of the stimulus-secretion coupling process leading to aldosterone secretion from the calf adrenal glomerulosa cells as evoked by angiotensin II (AII) and potassium (K+). The roles of Ca2+, calmodulin and protein kinase C in the sustained phase rather than initiation of aldosterone secretion were of special interest. Our investigations revealed that the reduction of extracellular Ca2+ by EGTA or interruption of Ca2+ influx by nitrendipine at various time points after stimulation with either AII or K+ markedly compromised aldosterone secretion. Calmodulin inhibitors, calmidazolium and W-7 reduced aldosterone secretion profoundly. Agonists of protein kinase C, phorbol ester or diacylglycerol analogues failed to stimulate aldosterone secretion while the protein kinase C inhibitor, H-7, only partially inhibited aldosterone secretion at a concentration which completely inhibited protein kinase C activity. Calmodulin inhibitors produced significantly greater inhibition of aldosterone secretion than inhibitors of protein kinase C.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
Erythromelalgia as a form of neuropathy.
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Adult↗
Teaching pathology to medical students in the 1990s: a 1989 symposium of the Association of Pathology Chairmen.
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Curriculum↗
Modulation of luteinizing hormone-stimulated inositol phosphate accumulation by phorbol esters in bovine luteal cells.
The present studies were conducted to evaluate the effects of protein kinase C activators on the inositol phospholipid-phospholipase C second messenger system in isolated bovine luteal cells. This report describes the effects of phorbol esters on inositol phosphate accumulation in LH- and prostaglandin F2 alpha (PGF2 alpha)-stimulated bovine luteal cells. Corpora lutea of early pregnancy were dispersed with collagenase and luteal cells were prelabelled for 3 h with [3H]inositol. Inositol phosphates produced in response to LH or PGF2 alpha were analyzed by ion exchange column chromatography. The tumor promoter and protein kinase C activator 12-O-tetradecanolyphorbol 13-acetate (TPA) had no effect on basal levels of inositol phosphates but inhibited LH-stimulated accumulation of inositol mono-, bis-, and trisphosphates by 72%, 68%, and 65%, respectively. TPA reduced the response to maximally effective concentrations of LH and tripled the concentrations of LH required to evoke half-maximal accumulation of inositol mono-, bis-, trisphosphates. The inhibitory effects of TPA were rapid (5 min) whether added before or after treatment with LH. Treatment with TPA also reduced (58%) the initial phase of intracellular calcium mobilization in LH-treated cells. The inhibitory effects of TPA were not associated with acute reductions in [3H]inositol incorporation, [3H]inositol phospholipid levels, cAMP levels, or progesterone accumulation in control or LH-stimulated luteal cells. The effects of phorbol esters were concentration dependent and specific for active tumor promoters with 10-50 nM TPA producing maximal inhibitory effects. A synthetic diacylglycerol, 1-oleyl-2-acetylglycerol, mimicked the inhibitory effects of TPA. In contrast, pretreatment with a physiological activator of protein kinase C, PGF2 alpha, had no effect on LH-stimulated inositol phosphate accumulation. The inhibitory effects of TPA could not be explained by a generalized inhibition of phospholipase C or G-proteins since the accumulation of inositol phosphates in PGF2 alpha- and NaF-treated cells was not inhibited by TPA. These results demonstrate that tumor promoting phorbol esters modulate the inositol phospholipid-phospholipase C transmembrane signaling system in LH-stimulated bovine luteal cells. The results suggest that phorbol esters may alter the coupling of the LH-receptor complex to phospholipase C. These findings implicate protein kinase C in the regulation of transmembrane signaling in the bovine corpus luteum.
Animals↗
Autoantibodies to human stress proteins. A survey of various rheumatic and other inflammatory diseases.
Unselected sera from patients with various rheumatic, inflammatory bowel, and autoimmune skin diseases (n = 268) were examined against human cell lysate by immunoblotting procedures, to determine the prevalence of autoantibodies to stress proteins (heat-shock proteins) hsp60 (homolog of Escherichia coli groEL and mycobacterial 65K antigens), hsp73, and hsp90. Using standard, sensitive and specific assay conditions, IgG and IgM autoantibodies to these stress proteins were not demonstrable, or were detected infrequently, in sera from control subjects (n = 36) and from patients with rheumatoid arthritis, Sjögren's syndrome, ankylosing spondylitis, Reiter's syndrome, systemic lupus erythematosus, and systemic sclerosis. Autoantibodies to hsp60 were relatively more common (greater than or equal to 20% of sera) in patients with mixed connective tissue disease, polymyositis/dermatomyositis, psoriatic arthritis, inflammatory bowel disease, epidermolysis bullosa acquisita, and bullous pemphigoid. Anti-hsp73 autoantibodies were detected in 20% or more of the sera from patients with Lyme disease and ulcerative colitis. Taken together, these data extend the spectrum of autoimmune and inflammatory diseases in which humoral anti-stress protein autoreactivity develops. However, the paucity of humoral autoreactivity to stress proteins in patients with systemic lupus erythematosus and rheumatoid arthritis argues against a direct role of anti-stress protein autoantibodies in the pathogenesis of these disorders.
Autoantibodies↗
Treatment options for the neonate with hypoplastic left heart syndrome.
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Cardiac Surgical Procedures↗
Prostaglandin F2 alpha stimulates inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate formation in bovine luteal cells.
The present studies were conducted to further evaluate inositol phosphate formation and metabolism in prostaglandin F2 alpha (PGF2 alpha)-stimulated bovine luteal cells. Corpora lutea were dispersed with collagenase, and luteal cells were prelabeled for 3 h with [3H]inositol. Inositol phosphates produced in response to PGF2 alpha were analyzed by ion exchange column chromatography and HPLC. Time-course experiments revealed that significant increases in inositol trisphosphate (InsP3) were apparent within 5 sec of incubation with PGF2 alpha. Increases in inositol bisphosphate (InsP2) were also apparent within 5 sec. InsP1 and InsP4 were observed after a short (5-sec) lag period. HPLC revealed that PGF2 alpha provoked rapid (5 sec) increases in inositol 1,4,5-trisphosphate (Ins 1,4,5-P3), which was rapidly converted to inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-P4) and inositol 1,3,4-trisphosphate (Ins 1,3,4-P3). The primary inositol bisphosphate isomer present in PGF2 alpha-stimulated bovine luteal cells was inositol 1,4-bisphosphate (Ins 1,4-P2), with lesser amounts of Ins 1,3-P2. Inositol monophosphates were also increased. These findings were confirmed in studies in which the metabolism of purified [3H]Ins 1,4,5-P3 was followed temporally in saponin-permeabilized bovine luteal cells. Additional studies demonstrated the presence of an enzyme, InsP3-3-kinase, in the cytosolic fraction of bovine corpora lutea. InsP3-3-kinase phosphorylated Ins 1,4,5-P3 to form Ins 1,3,4,5-P4. The activity of InsP3-3-kinase was calcium dependent and was enhanced by calmodulin at low calcium concentrations. Calmidazolium, a calmodulin inhibitor, reduced InsP3-3-kinase activity in a concentration-dependent manner. These results demonstrate the presence of multiple polyphosphorylated inositol phosphates in PGF2 alpha-stimulated bovine luteal cells. The isomers were formed via the action of a specific calcium/calmodulin-regulated kinase (InsP3-3-kinase), which phosphorylated Ins 1,4,5-P3 during agonist-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate. These data suggest that the inositol tris/tetrakisphosphate pathway is an important sequelae to PGF2 alpha-stimulated inositol phospholipid hydrolysis, and that the pathway may be activated during agonist-mediated calcium mobilization.
Animals↗
A novel mechanism for the induction of aromatase in ovarian cells in vitro: role of transforming growth factor alpha-induced protein tyrosine kinase.
In the developing follicle, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are the primary stimulators of steroidogenesis in granulosa and theca cells. The steroidogenic actions of both these gonadotropins are largely if not exclusively mediated through cAMP. Previous studies have shown that EGF and TGF alpha do not affect basal estrogen production but attenuate FSH-stimulated estrogen production in vitro in rat granulosa cells. Here we present evidence that TGF alpha stimulates basal estrogen production in prepubertal porcine ovarian granulosa and theca cells in culture under defined conditions. In granulosa cells, TGF alpha is more potent than FSH in stimulating estrogen production. LH does not stimulate estrogen production in prepubertal porcine theca cells but rather attenuates that stimulated by TGF alpha. Treatment of follicular cells with genistein (inhibitor of protein tyrosine kinase) attenuates TGF alpha-induced estrogen biosynthesis suggesting that the action of TGF alpha is mediated through protein tyrosine kinase. These studies provide evidence for an alternative cAMP-independent and TGF alpha-induced tyrosine kinase-dependent mechanism for the induction of ovarian aromatase.
Animals↗
Rheumatoid factor, cryoglobulinemia, anti-DNA, and renal disease in patients with systemic lupus erythematosus.
We retrospectively analyzed the relationship between rheumatoid factor (RF) and renal disease in 102 patients with systemic lupus erythematosus (SLE). We found a significant negative association between detectable RF at any time in a patient's course and clinically significant renal diseases. Multivariate analysis indicates that RF and cryoglobulins, operating independently, have a significant and opposite association with the development of renal disease in patients with SLE. These associations appear to be unrelated to the presence or absence of anti-ds-DNA (anti-DNA). Patients with SLE who are RF negative and cryoglobulin positive are likely to develop renal disease whereas those who are RF positive and cryoglobulin negative are very unlikely to do so. The addition of RF and cryoglobulin determinations to the data base of patients with SLE appears to be clinically useful.
Antibodies, Antinuclear↗
Differential effects of calcium on progesterone production in small and large bovine luteal cells.
We studied the effects of calcium (Ca2+) ions in progesterone (P) production by separated small and large luteal cells. Corpora lutea were collected from 31 heifers between days 10 and 12 of the estrous cycle. Purified small and large cells were obtained by unit gravity sedimentation and flow cytometry. P accumulation in cells plus media was determined after incubating 1 x 10(5) small and 5 x 10(3) large cells for 2 and 4 h respectively. Removal of Ca2+ from the medium did not influence basal P production in the small cells (P greater than 0.05). However, stimulation of P by luteinizing hormone (LH), prostaglandin E2 (PGE2), 8-bromo-cyclic 3',5' adenosine monophosphate (8-Br-cAMP) and prostaglandin F2 alpha (PGF2 alpha) was impaired (P less than 0.05) by low Ca2+ concentrations. LH and PGE2-stimulated cAMP production was not altered by low extracellular Ca2+ concentrations, and PGF2 alpha had no effect on cAMP. In contrast, basal as well as LH and forskolin-stimulated P production were attenuated (P less than 0.05) in Ca2(+)-deficient medium in the large cells. However, P production stimulated by 8-Br-cAMP was not altered in Ca2(+)-deficient medium. Steroidogenesis in large cells was also dependent on intracellular Ca2+, since 8-N, N-diethylamineocytyl-3,4,5-trimethoxybenzoate (TMB-8), an inhibitor of intracellular Ca2+ release and/or action, suppressed (P less than 0.05) basal, LH and 8-Br-cAMP stimulated P. In contrast, basal P in small cells was not altered by TMB-8; whereas LH-stimulated P was reduced 2-fold (P less than 0.05). The calcium ionophore, A23187, inhibited LH-stimulated P in small cells and both basal and agonist-stimulated P in large cells. These studies show that basal P production in small cells does not require Ca2+ ions, while hormone-stimulated P production in small cells and both basal and hormone-stimulated P in large cells do require Ca2+. The inhibitory effect of Ca2+ ion removal was exerted prior to the generation of cAMP in the large cells, but distal to cAMP generation in hormone-stimulated small cells. The calmodulin/protein kinase C antagonist, W-7, also inhibited both basal and hormone-stimulated P production in both small and large luteal cells, indicating that P production in luteal cells also involves Ca2(+)-calmodulin/protein kinase C-dependent mechanisms.
8-Bromo Cyclic Adenosine Monophosphate↗
External calcium is required for activation of phospholipase C by angiotensin II in adrenal glomerulosa cells.
Previous studies have shown that external calcium (Ca2+) is required for the effects of angiotensin II (AII) on aldosterone secretion in adrenal glomerulosa zone. Using bovine adrenal glomerulosa cells prepared by collagenase dispersion, we examined whether external Ca2+ is required for the activation of phospholipase C by AII. Adrenal glomerulosa cells were exposed to Ca-EGTA buffered media to provide accurate estimates of external free Ca2+ concentrations. Phospholipase C activation was evaluated by measurement of inositol phosphates production. At 0.1 microM Ca2+ and less, sustained AII effects on inositol monophosphate (IP), inositol bisphosphate (IP2) and inositol trisphosphate (IP3) were markedly inhibited. Increasing the Ca2+ concentration to 50 microM or greater fully restored AII-induced inositol phosphates production. AII-induced increases in cytosolic Ca2+ measured by Quin-2 fluorescence, were diminished at lower external Ca2+ concentrations. Treating adrenal glomerulosa cells with Chelex-100, a strong Ca2+ binding resin, blocked early activation of phospholipase C by AII. Inhibition of IP3 production was also observed when inhibitors of Ca2+ movement across the plasma membrane were used, viz., La2+, TMB-8 and nifedipine. The requirement for Ca2+ during AII-induced activation of phospholipase C may be explained, at least partly by a requirement for Ca2+ at a site between the AII receptor and Phospholipase C.
Aldosterone↗