Effect of hypothermia on insulin-receptor interaction in different rat tissues.

Experimental hypothermia caused extensive changes in the number of both classes of insulin receptors in different rat tissues. In the liver, the number of high affinity insulin receptors (HAIRs) decreased by 50% (from 25.3 to 12.6 fmol/mg membrane protein), whereas number of low affinity insulin receptors (LAIRs) was almost unchanged in comparison to normothermic animals (5.63 and 4.39 pmol/mg, respectively). In the adipose tissue, number of both classes was reduced--HAIRs by 81% (from 24.0 to 4.50 fmol/mg) and LAIRs by 92% (from 16.0 to 1.29 pmol/mg). In the skeletal muscle, capacity of HAIRs was not changed (16.2 and 19.3 fmol/mg in normo- and hypothermic animals, respectively), whereas number of LAIRs increased by 150% (from 6.65 to 16.6 pmol/mg). Hypothermic rats also showed lower amount (by 85%) of LAIRs in the heart muscle (9.37 and 1.43 pmol/mg in control and experimental animals, respectively). Simultaneously, no significant changes were found in HAIRs (16.3 and 11.9 fmol/mg, respectively) and LAIRs (4.43 and 3.88 pmol/mg, respectively) in the brain. These differences in insulin receptors responses to hypothermia may reflect different physiological role of insulin in the regulation of target cell metabolism and/or the differences in tissue distribution of the insulin receptor isoforms.

The influence of CYP2D6 polymorphism on the antiarrhythmic efficacy of propafenone in patients with paroxysmal atrial fibrillation during 3 months propafenone prophylactic treatment.

OBJECTIVE: Propafenone (PPF) is an antiarrhythmic, Class Ic agent. Its metabolism is genetically controlled by a cytochrome P450 isoenzyme named CYP2D6, which shows polymorphism in human population. The aim of this paper was to determine the correlation between the antiarrhythmic efficacy of PPF and the oxidation phenotype. SUBJECTS AND MATERIAL: The study group consisted of 42 patients, aged 36 to 75 years, suffering from paroxysmal atrial fibrillation (AF). The oxidation phenotype was described by the metabolic ratio (MR) of sparteine. The MR value separated the group of poor metabolizers (MR > 20) from the group of extensive metabolizers (MR < 20) with the subgroup of very extensive metabolizers (MR < 1). METHOD: The study was conducted during a 3-month PPF therapy for the prophylaxis of paroxysmal atrial fibrillation. PPF was given orally, 300-450 mg/day. The oxidation phenotype was checked prior to the administration of PPF. Serum concentration of PPF at 7, 11 days and the end of PPF therapy were determined. Statistical analysis of data was performed with the chi2 test and the Pearson's correlation methods. RESULTS: In the group of 42 patients, PPF therapy was 100% effective in poor metabolizers (PM). In extensive metabolizers (EM), 61% efficacy was observed with efficacy 0% in very extensive metabolizers (VEM). The correlation between oxidation phenotype and the ability to maintain sinus rhythm (SR) was statistically significant (r = 0.414, p < 0.05). CONCLUSIONS: The antiarrhythmic efficacy of propafenone depends on the oxidation phenotype; 100% efficacy occurred in the group of poor metabolizers whereas PPF, at the dose tested, was ineffective in very extensive metabolizers.

Insulin receptor--structural and functional characteristics.

The insulin receptor is a complex multifunctional protein located on the cell surface within the fluid mosaic matrix of the plasma membrane. Its ability to bind insulin is determined by structural and spatial specificity, high affinity and reversibility. Insulin action at the cellular level can be considered in three stages. The first stage includes the insulin receptor itself, the insulin substrate (IRS-1) and the molecules that interact with IRS-1. The second stage is that of cascade phosphorylation and dephosphorylation. The third stage concerns the final biological effects of the insulin cascade. The biological specificity of insulin binding and heterogeneity of insulin action in different cells has been well documented. This review intends to summarize the available data of structural and functional characteristics of insulin receptor.

Age dependent changes of insulin receptors in rat tissues.

Aging is associated with insulin resistance but the exact molecular mechanism is still unknown. Tissue insulin resistance can be evoked by the decreased sensitivity to insulin, the decreased responsiveness to hormone or both. As the first step in insulin action is its binding to alfa subunits of the receptor we, therefore, studied the insulin binding kinetics in plasma membranes of the liver, heart and skeletal muscle in order to establish whether their ability to bind the hormone is altered with aging. Plasma membranes were prepared and purified according to Havrankowa and binding assay was performed using (125I)-iodoinsulin. The kinetic parameters of the hormone-receptor interaction were analysed by the method of Scatchard using the LIGAND-Pc v.3.1. computer program. The binding potency of insulin was calculated as IC50 using ALLFIT-Pc v.2.7. computer program. We have shown that there are striking differences in insulin binding kinetics in newborn and old rats, depending on kind of tissue tested. The liver plasma membranes ability for insulin binding, number of high (HAIR) and low (LAIR) affinity insulin receptors, values of the dissociation constants and products of association constants and number of insulin receptors, were almost the same, being not dependent on age of the rats. By contrast, there is less high affinity insulin receptors in skeletal muscle of the old animals. The most dramatic changes in insulin binding occur in the heart where both high and low affinity insulin receptors are greatly affected by aging. Our results indicate that the response of the three tissues tested to hyperglycemia and hyperinsulinemia, observed in the old rats, has not been identical and probably can be accounted for by the different distribution of insulin receptor isoforms in the liver, heart and skeletal muscles as shown recently by Vidal et al.

Characteristics of insulin receptor binding to various rat tissues.

The first step in insulin action is its specific binding to alpha-subunits of the receptor in the plasma membrane. Rats of Wistar strain are commonly used as laboratory animals but there are no data comparing insulin binding by various rat tissues. We studied the insulin binding kinetics in plasma membranes isolated from hearts, livers, brains, skeletal muscles, adipose tissue, thymus and testes in order to compare their ability to bind 125I-insulin and to test which membrane preparation is most useful and convenient for such a study. The dissociation constant (Kd) and the quantity of receptors measured as a binding capacity were determined by the Scatchard method using the LIGAND computer program whereas the binding potency of insulin was calculated as IC50 using the ALLFIT computer program. We also introduced the product of Ka x R50 (affinity constant multiplied by binding capacity) as an index which describes the functional features of insulin receptors taking into account both number of insulin receptors and their affinity. Taking all the parameters of insulin binding tested together we can conclude that the liver and, to some extent, adipose tissue may provide a useful model for studying hormone-receptor interaction. By contrast, to the group of rat tissues responding rather poorly to insulin belong thymus and testis.

Multicultural maternal and child health outreach: Washington State strategies to assure access for Asian and Pacific Islander women and children.

This article outlines some of the barriers to health care experienced by Asian and Pacific Islander Communities. The authors then describe a number of strategies the Washington State Department of Health has used to reduce cultural and linguistic barriers to health care. As a state health agency, the Department has promoted accessible programs through mechanisms such as improved data collection, culturally competent staff, targeted outreach, and development of partnerships with community organizations and other agencies to promote culturally accessible health care delivery.

Potential role in development of the major cysteine protease in larvae of the brine shrimp Artemia franciscana.

Encysted embryos and larvae of the brine shrimp Artemia franciscana contain a cysteine protease which represents over 90% of the protease activity in these organisms. We have used immunocytochemical methods to determine the localization and potential role of the cysteine protease in development of young larvae. In prenauplius larvae, there is intense staining for the protease on the basal side of the epidermal layer in the posterior region and diffuse staining for the protease throughout the embryo. In first instar larvae, cysteine-protease staining becomes intense in the midgut-forming area where a reticulum-like pattern emerges in cells with an abundance of yolk platelets. Cysteine-protease staining in second instar larvae becomes intense in the apical side of epidermal cells and in the basal and apical zones of midgut cells. Subcellular localization of the protease in the epidermis and midgut of young larvae using immunogold electron microscopy suggests that most is located in the cytosol and extracellular matrix adjacent to these cells. Addition of cysteine-protease inhibitors to the growth medium, especially the fluoromethyl ketone Z-Phe-Ala-CH2F, inhibits growth and segmentation of the thorax. Collectively, these observations suggest that the major cysteine protease in embryos and larvae functions in yolk utilization, as a hatching enzyme, in apolysis during the molt cycle, and as a digestive enzyme when the swimming larvae begin to feed.