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D F Sellitti

Publications and source records attributed to D F Sellitti.

26 records · Page 2Linked to original sources
PubMed1987

Interaction of amiodarone and desethylamiodarone with solubilized nuclear thyroid hormone receptors.

The mechanisms of action of the potent antiarrhythmic drug amiodarone are unknown. However, amiodarone and its abundant metabolite, desethylamiodarone, bear a striking structural resemblance to thyroid hormones. In addition, certain cardiac electrophysiologic effects of amiodarone treatment are similar to those of hypothyroidism. These facts suggest that amiodarone or desethylamiodarone could be acting, in part, by blocking thyroid hormone action. Because thyroid hormones are known to act through nuclear receptor proteins, the binding of amiodarone and desethylamiodarone was measured to nuclear extracts derived from human lymphocytes, bovine atrium and ventricle and rat liver. The capacity of increasing concentrations of amiodarone and desethylamiodarone nuclear extracts to block receptor binding of radiolabeled triiodothyronine (T3) in a standard in vitro competition assay was tested. Nuclear extracts demonstrated only minimal binding to amiodarone. However, all receptor preparations had substantial affinities (KD) for the desethyl analog: lymphocyte, 8.6 microM; atrium, 35.0 microM; ventricle, 26.9 microM and liver, 8.6 microM. Desethylamiodarone accumulates in very large quantities in parenchymatous organs during long-term amiodarone treatment. Taking its usual therapeutic serum level (about 4 microM or 2.7 micrograms/ml) as an estimate of intranuclear concentration, desethylamiodarone would partially saturate nuclear thyroid hormone receptors in several different tissues, including the heart. Thus, amiodarone treatment may exert some of its electrophysiologic effects by metabolic conversion to desethylamiodarone. This metabolite may then exclude thyroid hormone from nuclear receptor sites within the myocardium.

Amiodarone↗
PubMed1985

Antibodies to nuclear thyroid hormone-binding proteins. Antibody characterization and immunofluorescent localization.

To further investigate the mechanism by which thyroid hormones regulate target cell function, we have prepared and partially characterized antibodies to highly purified nuclear thyroid hormone-binding proteins (NTBP). NTBPs were prepared from bovine liver nuclear extracts by bio-specific elution from an affinity gel containing immobilized 3,5,3'-triiodo-L-thyronine (T3). Antibodies (Ab) raised to NTBP in BALB/c mice were assayed for Ab-NTBP complex formation on HPLC TSK SW3000 molecular exclusion gels and found to be species-specific and non-cross-reactive with serum thyroid hormone-binding proteins. Most of the antibody activity was directed against two fractions of molecular weight (MW) 89 000 and 53 000, which were associated with thyroxine (T4)-binding activity. The 89 000 D T4-binding activity was shifted to a higher MW complex when incubated with specific antibody. Indirect immunofluorescence showed antibody activity against discrete, clumped chromatin sites, nuclear envelope and plasma membrane in hepatocytes. Intense fluorescence was also observed in the cells lining the hepatic sinusoids and in the cytoskeleton of bovine aortic endothelial cells in culture. The data suggest that thyroid hormone target cells contain extranuclear loci that share antigenic sites with NTBP and may also represent specific NTBP-like sites of thyroid hormone binding.

Animals↗
PubMed1983

Nuclear thyroid hormone receptors in C3H/HeN mouse mammary glands and spontaneous tumors.

Saturable, high-affinity binding sites for 3,5,3'-triiodo-L-thyronine (T3) were identified in isolated nuclei and solubilized chromatin extracts of mammary glands, spontaneous mammary tumors, and liver from C3H/HeN mice. Receptor concentration in whole mammary gland nuclei (254 fmol/mg DNA) was only about one-half that of mouse liver nuclei (536 fmol/mg DNA), but in molecular weight (55,000) and in their affinity for various thyroid hormone analogues, the binding was essentially identical. Saturation analysis of T3 binding in a series of individual spontaneous mammary tumors and pooled lactating mammary glands indicated that the concentrations of T3-binding sites of the mammary gland are conserved in the transition to neoplasms and are somewhat increased in the largest tumors. Thyroxine binding was identical in capacity to T3 binding in mammary gland nuclei and nuclear extract but showed a higher binding capacity than did T3 in the largest tumors. High-performance molecular exclusion chromatography did show a difference between mammary gland and liver in the distribution of competible [125I]T3 binding between two macromolecular forms; the excluded peak (Mr greater than 450,000) comprised 56% of the T3 binding in the liver but only 9% in the mammary gland with the included peak (Mr 55,000) contributing the balance of binding in each case. Spontaneous mammary tumor resembled the mammary gland in the macromolecular distribution of specific T3 binding (16% excluded). Thymidine uptake showed only a modest decrease in the larger tumors (greater than 2.0 g), while nuclear histone acetylase activity was significantly decreased in this group. Neither measurement showed a significant correlation with T3 or thyroxine binding capacity.

Animals↗
PubMed1981

Effect of 3,5,3'-triiodo-L-thyronine on the incidence and growth kinetics of spontaneous mammary tumors in C3H/HeN mice.

The present study compares the incidence and growth kinetics of spontaneous mammary tumors in 3,5,3'-triiodo-L-thyronine (T3)-treated (0.7 microgram/day, i.p.) C3H/HeN retired breeder mice with tumors occurring spontaneously in this strain (0.15 M NaCl, i.p.). T3 treatment markedly increased the rate of tumor incidence but had no effect on tumor growth rate as measured by tumor doubling time. A comparison of tumor labeling index and mitotic index between the two groups showed no difference. A histological comparison of the mammary glands in the two groups showed no significant difference in number of hyperplastic alveolar nodules. However, ductal-alveolar development was more pronounced in the 0.15 M NaCl-treated control group; consistent with this observation was the finding of lower levels of serum prolactin in the T3-treated groups. Since mammary tumorigenesis was increased in T3-treated mice in spite of lower levels of serum prolactin, a well-known promoter of spontaneous mammary tumors in mice, a direct role for T3 in the process of tumor formation is suggested.

Animals↗
PubMedDate not supplied

Glutamine-dependent changes in gene expression and protein activity.

The functions of glutamine are many and include, substrate for protein synthesis, anabolic precursor for muscle growth, acid-base balance in the kidney, substrate for ureogenesis in the liver, substrate for hepatic and renal gluconeogenesis, an oxidative fuel for intestine and cells of the immune system, inter-organ nitrogen transport, precursor for neurotransmitter synthesis, precursor for nucleotide and nucleic acid synthesis and precursor for glutathione production. In the present review information on the mechanism of glutamine action is presented. This amino acid has been shown to regulate the expression of several genes (such as p47phox, p22phox, gp91phox, alpha-actin and fibronectin) and activate several proteins (such as ASK1, c-myc, c-jun and p70s6k).

Animals↗
PubMedDate not supplied

Thyroidal ANF: a possible mediator of autocrine regulation in the porcine thyroid gland.

Atrial natriuretic factor immunoreactivity (ir-ANF) was examined in thyroid tissue sections and cultured thyroid cells using immunohistochemical staining with a monoclonal anti-ANF antibody. Localization of ir-ANF in perinuclear granules in cultured cells and in the basal region of follicular cells in sectioned tissue suggests that ir-ANF is a basally secreted product. Thyroidal ir-ANF was also characterized using reversed phase high performance liquid chromatography (RP-HPLC) of acidic thyroid extracts. An ir-ANF peak coeluting with synthetic rat ANF(99-126) suggests that thyroidal ir-ANF may be identical in form to circulating atrial ANF. However, the detection of ir-ANF in cultured thyroid cells confirms that the immunoreactivity is locally produced. Saturation analysis revealed high affinity ANF receptors (Kd = 0.1 nM; MBC = 17.2 fmol/mg protein) on these cultured cells, and a competition study demonstrated the ability of extracted thyroidal ir-ANF to inhibit 125I rat ANF binding to the membrane receptors. The evidence presented here suggests that ir-ANF in the thyroid may be secreted locally to exert an autocrine effect on neighboring follicular cells.

Animals↗
PubMedDate not supplied

Renal expression of two 'thyroid-specific' genes: thyrotropin receptor and thyroglobulin.

Numerous renal abnormalities accompany thyroid disease, most of which have been ascribed to the effects of thyroid hormone on renal metabolism. In the present report, we investigate the renal expression of the nominally thyroid-specific proteins, thyroid-stimulating hormone (TSH) receptor (TSHR) and thyroglobulin (Tg), as potential links between renal and thyroid function. The expression of TSHR has been identified in several extrathyroidal tissues, but its presence in the kidney remains controversial. We have used reverse-transcriptase polymerase chain reaction and DNA sequencing to demonstrate the presence of TSHR transcript in human and mouse kidney, in a primary culture of human kidney, and in a green monkey kidney epithelioid cell line. Furthermore, human kidney cells responded to TSH with a 2.5- fold increase in intracellular cyclic adenosine monophosphate, suggesting the presence of functional TSHR protein. Comparison of renal expression of TSHR in a bovine growth hormone transgenic mouse model of progressive glomerulosclerosis with control mice suggested increased TSHR transcript in the renal cortex of transgenic animals. TSHR transcript was also detected in mouse mesangial cells in vitro which responded to TSH with significant increases in the formation of three-dimensional hillhocks. Polymerase chain reaction also confirmed the presence of Tg transcript in human and mouse kidneys and in mouse mesangial cells, but no effect of either TSH or cyclic adenosine monophosphate on Tg transcript levels could be discerned. Immunofluorescent staining with a monoclonal anti-Tg antibody identified positive staining in the cytoplasm of mesangial cells. These data suggest that the kidney is capable of expressing the thyroid-specific genes, TSHR and Tg, which could conceivably mediate effects of thyroid disease in the kidney.

Animals↗