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The in vivo effects of the insulin-like growth factor-II (IGF-II) on glucose metabolism is not yet well defined. To assess the acute effect of IGF-II administration on whole body glucose utilization and hepatic glucose production, we used the well-established euglycemic clamp technique and compared the effects in awake cannulated rats with those of insulin. Each animal underwent several 90-min euglycemic studies, alternating between IGF-II and insulin. Following IGF-II infusion, tissue glucose uptake was increased to 9.8 +/- 0.6 mg/kg/min (mean +/- SEM), which represented only 14% of the effect of insulin, despite the molar plasma concentration ratio of insulin: IGF-2 being 1:460. IGF-II and insulin infusion reduced hepatic glucose output by 49 and 75%, respectively. Thus, IGF-II, administered acutely, affects glucose homeostasis in a manner very similar to insulin, probably via the insulin receptors, although with significantly lower potency.

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The non-obese diabetic mouse is a model of spontaneous insulin-dependent diabetes as a result of autoimmune destruction of pancreatic beta cells, similar to the disease seen in human Type I diabetes. This mouse strain develops glomerular lesions reminiscent of those seen in human disease. The study presented here investigated the changes in renal insulin-like growth factor (IGF) system in hyperglycemic non-obese diabetic mice. Female non-obese diabetic mice and their age- and sex-matched controls were euthanized 4 days, 2 wk, and 4 wk after the onset of glycosuria. Kidney weight increased in diabetic mice, beginning at 2 wk after the onset of glycosuria. This renal hypertrophy was associated with an increase in renal extractable IGF-I protein. However, a decrease in IGF-I mRNA was observed at the same time. Serum IGF-I levels remained stable after 2 wk of diabetes and decreased at 1 month. No change was detected in renal IGF-I receptor mRNA levels. Renal cortical IGF binding protein (IGFBP)-1 mRNA levels were increased. Ligand blot analysis revealed a significant increase in serum and renal 30-kd IGFBP and a decrease in serum and kidney IGFBP-3 and IGFBP-4 at 30 days of diabetes. Insulin therapy prevented the increases in kidney weight, renal IGF-I, and 30-kd IGFBP, but did not reverse the decreased serum IGF-I levels observed at 1 month of diabetes. In summary, renal hypertrophy in non-obese diabetic mice is associated with a persistent accumulation of renal IGF-I and, IGFBP-1. These changes were partially reversed with insulin therapy, which did not correct the hyperglycemia, suggesting an important role for insulin deficiency in mediating these changes in the IGF system. These findings suggest that the IGF system may play a potential role in the development of diabetic nephropathy.

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Several studies have supported the idea that LH-releasing hormone (LHRH) antagonists have a direct effect on mammary tumor cells. In this study, we have evaluated the potential role of the insulin-like growth factors (IGFs) on the growth of MCF-7 mammary tumor cells and the effect of LHRH analogs on IGF action. The mitogenic effects of IGF-I, IGF-II, and insulin were compared. IGF-I was found to be 3 times more potent than IGF-II and 30 times more potent than insulin, suggesting that the effects of these growth factors are mediated by the IGF-I receptor. IGFs released by MCF-7 cells were measured by specific RIA after acid extraction and chromatography, so as to avoid the interference of IGF-binding proteins. MCF-7 cells secreted IGF-II, but not IGF-I. Estradiol (10(-9) mol/L) stimulated IGF-II release; this release preceded the effect of estradiol on cell growth. The LHRH antagonist [Ac-D-Nal(2)1,D-Phe(4Cl)2,D-Pal(3)3,D-Cit6,D-Ala10] LHR H (SB-75, CETRORELIX) inhibited basal, estrogen-induced, and IGF-induced growth. Moreover, this antagonist almost completely inhibited IGF-II release from MCF-7 cells. This effect preceded the inhibition of tumor cell growth. We conclude that a LHRH antagonist can inhibit the growth of breast tumors by interfering with the autocrine action of IGF-II and by directly inhibiting the growth stimulatory effect of IGFs.

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Ethanol stimulates the Na(+)-dependent Ca2+ efflux in brain mitochondria and inhibits the Na(+)-independent Ca(2+)-efflux. Here, we studied the effects of n-alkanols on the various Ca2+ transport processes in brain mitochondria. Only short-chain alcohols (i.e. methanol, ethanol and propanol) stimulated Na+/Ca2+ exchange. The inhibition of H+/Ca2+ exchange was significant only with ethanol. Short-chain alcohols inhibit while long-chain alcohols activate the cyclosporin-sensitive Ca(2+)-efflux. These data suggest that the mechanism of the alkanols' effects on Na+/Ca2+ exchange, H+/Ca2+ exchange and the cyclosporin sensitive pore are entirely different. Alkanols have no effect on the electrogenic Ca2+ uniporter. Ethanol did not affect the apparent K0.5 for Na+ (7.5 mM) of the Na+/Ca2+ exchange. Similarly, the magnitude of the effect of ethanol did not depend on matrix Ca2+ concentration, suggesting that short-chain alkanols do not stimulate the rate of Na+/Ca2+ exchange by increasing the affinity of the carrier to Ca2+in or Na+out. High concentrations of K+, Mg2+ and Ca2+ enhanced the ethanol effect. It is possible that high surface potential attenuates the effect of ethanol. It is suggested that ethanol stimulation of Na+/Ca2+ exchange depends on the modulation of the surface dielectric constant.

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Ethanol, at low concentrations, specifically stimulates the Na(+)-dependent Ca2(+)-efflux in brain mitochondria. In addition, at higher concentrations, ethanol inhibits the Na(+)-independent Ca2(+)-efflux. The electrogenic Ca(+)-uptake system is not affected by ethanol. The specific stimulation of Na+/Ca2+ exchange reaches a maximum of 60% stimulation, with half-maximal stimulation at 130 mM ethanol. The inhibition of the Na(+)-independent efflux is proportional to the ethanol concentration, becoming significant only above 200 mM, with 50% inhibition at 0.5 M. The inhibition of the Na(+)-independent efflux is, in large part, due to an inhibition of the activation of the Cyclosporin-sensitive pore. Long-term ethanol-feeding had no effect on the Ca2+ transport systems and their sensitivity to acute ethanol treatment. It is suggested that the stimulation of the Na(+)-dependent Ca2(+)-efflux, which is the dominant Ca2+ efflux pathway in brain mitochondria, contributes to the intoxicating effects of ethanol.

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The mechanism of the Na(+)-independent Ca2+ efflux system in mitochondria has not been elucidated as yet. With the aid of cyclosporin A, an inhibitor of the Ca2(+)-induced 'pore', and using a variety of inhibitors, uncouplers and ionophores, it is possible to demonstrate, unequivocally, that this process is driven by delta pH. The efflux is not affected by delta psi, thus suggesting an electroneutral Ca2+/2H+ exchange mechanism. Parallel measurements of the rate of Ca2+ efflux and delta pH, as modulated by valinomycin and nigericin, indicate that the rate of efflux is a function of the magnitude of delta pH.

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Spermine enhances electrogenic Ca2+ uptake and inhibits Na(+)-independent Ca2+ efflux in rat brain mitochondria. As a result, Ca2+ retention by brain mitochondria increases greatly and the external free Ca2+ level at steady-state can be lowered to physiologically relevant concentrations. The stimulation of Ca2+ uptake by spermine is more pronounced at low concentrations of Ca2+, effectively lowering the apparent Km for Ca2+ uptake from 3 microM to 1.5 microM. However, the apparent Vmax is also increased. At low Ca2+ concentrations, Ca2+ uptake is diffusion-limited. Spermine strongly inhibits Ca2+ binding to anionic phospholipids and it is suggested that this increases the rate of surface diffusion which reduces the apparent Km for uptake. The same effect could inhibit the Na(+)-independent efflux if the rate of efflux is limited by Ca2+ dissociation from the efflux carrier. In brain mitochondria (but not in liver) the spermine effect depends on the presence of ADP. In a medium that contains physiological concentrations of Pi, Mg+, K+, ADP and spermine, brain mitochondria sequester Ca2+ down to 0.1 microM and below, depending on the matrix Ca2+ load. Moreover, brain mitochondria under the same conditions buffer the external medium at 0.4 microM, a concentration at which the set point becomes independent of the matrix Ca2+ content. Thus, mitochondria appear to be capable of modulating calcium oscillations in brain cells.

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ADP greatly enhances the rate of Ca2+ uptake and retention in Ca2+ loaded mitochondria. Atractyloside, a specific inhibitor of the ADP/ATP translocator, completely inhibits the ADP effect, while bongkrekate, another specific inhibitor of the translocator enhances the effect of ADP. These results indicate that locking the ADP/ATP translocator in the M-state is sufficient to produce the ADP effect. Cyclosporin A, a specific inhibitor of the Ca2(+)-induced membrane permeabilization does not substitute for ADP, indicating that ADP directly affect the rate of electrogenic Ca2+ uptake. The effect of the translocator conformation on the rate of electrogenic Ca2+ uptake is independent of the concentration of Pi and is not caused by changes in membrane potential. However, locking the carrier in the M-state appears to increase the negative surface charge on the matrix face of the inner membrane. This may lead to an enhanced rate of Ca2+ dissociation from the electrogenic carrier at the matrix surface. The rate of Na(+)-independent Ca2+ efflux is only slightly inhibited by locking the carrier in the M-state, presumably due to the same mechanism. In the presence of ADP, Pi inhibits the Na(+)-independent efflux. In the presence of physiological concentrations of spermine, Pi and Mg2+, the rate of Ca2+ uptake, Ca2+ retention and Ca2+ set points depend sharply on ADP concentration at the physiological range of ADP. Thus, changes of cytosolic ADP concentration may lead to change in the rate of Ca2+ uptake by mitochondria and thus modulate the excitation-relaxation cycles of cytoplasmic free calcium.

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Adenine nucleotides (ADP greater than ATP) greatly enhance Ca2+ uptake and retention in rat brain mitochondria. In the presence of both spermine and ADP, brain mitochondria sequester Ca2+ down to cellular free Ca2+ levels, suggesting a role for mitochondria in modulating Ca2+ cycles in brain cells. Analysis of the effects of various inhibitors on Ca2+ uptake and efflux suggest that locking the ADP/ATP translocator in its M-state stimulates electrogenic Ca2+ uptake and, to a lesser extent, inhibits Ca2+ efflux. It is suggested that this effect is due to a modulation of the surface charge on the M-side which enhances Ca2+ dissociation from the carriers.

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Gonadotropin-releasing hormone (GnRH) analogs can cause regression of uterine leiomyomata. This effect is thought to be mediated by the inhibition of gonadotropin release and steroid synthesis. In the present study we examined the possibility that these analogs may also act directly on uterine leiomyomata. Specific binding sites for GnRH are present in myoma membranes, as 125I-Buserelin binding was displaced with equal efficiency by the superagonists, Buserelin and D-Trp6-GnRH, and by the antagonist Organon 30276, but not by unrelated peptides such as thyrotropin releasing hormone and oxytocin. A nonlinear Scatchard curve obtained for Buserelin specific binding suggests the presence of at least two binding sites, one of which exhibits a relatively high affinity for GnRH analogs (Kd of approximately 10(-8) M). Western blotting with a specific GnRH receptor antibody revealed the presence of a 60 kDa protein in myoma membranes. This protein has a similar molecular weight to the purified pituitary GnRH receptor. These results indicate, for the first time, the presence of specific binding sites for GnRH in uterine leiomyomata, suggesting a direct effect of GnRH analogs on this tissue.

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The effect of exogenously administered GH on somatostatin (SRIF) receptor regulation was studied in rat anterior pituitary membranes. A single class, high affinity specific receptor for SRIF was identified by binding studies with [125I-Tyr11]SRIF [binding capacity (mean +/- SD), 129.4 +/- 23.3 fmol/mg protein; binding affinity, 2.8 +/- 0.6 X 10(10) M-1]. A single injection of rat GH (150 micrograms) caused a significant reduction in capacity, but not in affinity, of SRIF receptors 2 and 6 h after injection (mean decrease, 23% and 24%, respectively) from that in controls. In contrast, mean SRIF binding capacity 24 h after a single injection of rat GH was increased 48% above control values, but affinity was unaffected. Measurement of membrane SRIF content indicated that these changes could not be explained by alterations in receptor occupancy. When rat GH was injected repeatedly for 3 days (150 micrograms/rat X day), the mean binding capacity, though not the affinity, of SRIF receptors was decreased 23% from that in controls 24 h after the last injection. The results can be explained by stimulation of SRIF release from the hypothalamus by GH and somatomedins, with subsequent internalization of the pituitary plasma membrane SRIF receptor. They suggest yet another level of neuroendocrine regulation of GH secretion.

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Tyrosine protein kinase activity was measured in membranes from DMBA-induced mammary tumors, with Angiotensin II as substrate. The apparent Km for the peptide was 3.3 mM. This enzymatic activity is inhibited by Ca+2; Mn+2 can replace Mg+2 with an increase in the Km for ATP from 47 /microM to 172 microM. The enzymatic activity was not affected by cyclic AMP but was inhibited in dose dependent manner by quercetin, a bioflavonoid which is known to inhibit proliferation of malignant cells in vitro.

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The competition of bromocriptine and lisuride hydrogen maleate (LIM) with estradiol binding to various tissues was evaluated by the dextran coated charcoal method. Bromocriptine and LIM competitively inhibited the binding of [3H] estradiol to its cytosolic receptors in rat uterine, pituitary and hypothalamic tissue and in DMBA induced mammary tumors. Ki was 2 X 10(-5) M for bromocriptine and 2 X 10(-4) M for LIM. Metoclopramide, dopamine and L-dopa had no significant effect on [3H] estradiol binding. The interaction of bromocriptine and LIM was specific for estrogen receptors. There was no interaction with progesterone receptors from rat uterus and pituitary and with testosterone receptors from rat epididymis and testis. When tested for estrogenity in the immature rat uterus, bromocriptine and LIM induced specific estrogen inducible proteins such as cytosolic estrogen and progesterone receptors. However, they do not affect the uterine/body weight ratio and peroxidase activity. A clear interaction of inhibitors (bromocriptine and LIM) of prolactine secretion, with cytosolic estrogen receptors from various tissues was shown. Some in vivo estrogenic effect was also demonstrated in the immature rat uterine system.

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The role of spironolactone in the aetiology of gynaecomastia was examined in terms of its ability to bind to the oestrogen receptor in cytosol, to cause specific oestrogenic effects in the absence of endogenous oestrogen and to be antioestrogenic in the presence of oestradiol. Tamoxifen, a non-steroidal antioestrogen, was chosen as an internal standard for comparison. Spironolactone and tamoxifen competitively inhibited the binding of oestradiol-17beta to its receptor in uterine and mammary cytosol, with inhibition constants of 2 x 10(-5) and 1 x 10(-7) mol/l respectively. To measure oestrogenic or antioestrogenic effects of the drugs five indices believed to be specific markers for oestrogen action were studied: uterine to body weight ratio, uterine protein content, oestradiol receptor in cytosol, progesterone receptor in cytosol and uterine peroxidase activity. Spironolactone, when administered for 3 successive days (40 microgram/day) to immature female rats, increased all of the five indices of oestrogen agonistic activity. The oestrogen-antagonistic properties of the drug were evaluated by comparing the oestradiol-injected group (5 microgram) to the oestradiol + spironolactone-injected group. A decrease was noted in all indices measured except for progesterone receptors in cytosol. Spironolactone appeared to be very similar to tamoxifen in its action both as an oestrogen and as an antioestrogen. The antioestrogenic effect of spironolactone cannot be explained by previously proposed mechanisms of action for the drug such as decreased synthesis of testosterone or inhibition of dihydrotestosterone binding to its receptor. These results suggest that spironolactone-induced gynaecomastia may be modulated by its action at both the oestrogen and dihydrotestosterone receptor in cytosol.

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49 unrelated subjects suffering from systemic scleroderma were typed for 28 HL-A antigens, without any particular significant association of an antigen with the disease or one of its manifestations being noted. In addition, 13 patients from the same family were genotyped for HL-A. Transmission of the disease through 4 generations does not seem to be linked to a particular haplotype and no pair of sibling HL-A identical patients were seen in the same generation. By contrast, two pairs of sibling patients were HL-A different. Nevertheless, other cases, and in particular familial, will be necessary before an association between the genes of susceptibility to S.S. and a gene in the chromosomal HL-A region may be definitely eliminated.

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