Insulin receptor binding to erythrocytes during normal pregnancy: an update of the method.

Normal values of the parameters of insulin receptors in erythrocytes were provided to make a control group throughout gestation, 24 h postpartum and six weeks after delivery with the aim of comparing them with other parameters with insulin receptor-related pathologies. Thus, one of the purposes of this study was the update of a method to calculate the parameters of insulin receptors in erythrocytes, carrying out several modifications that improved the assay: during binding studies incubation was in continuous rotation shaking, and increasing maximal insulin binding. Other modifications were the increase in the concentration of insulin 125I to 1 ng/mL, and the maximal concentration of unlabeled insulin, 100 ng/mL. Erythrocyte age was considered by the intracellular creatine content providing control values and allowing the normalization of the parameters of insulin receptor during gestation. Data obtained in this study indicated that changes at receptor binding level may be also considered to explain insulin resistance: week 28 showed maximal insulin secretion (16.70+/-1.44 microU/mL) whereas plasma glucose concentrations remained almost constant (91.14+/-2.37 mg/100 mL) with respect to the 1st and 2nd trimester of pregnancy (89.73+/-1.38 and 91.71+/-2.10 mg/100 mL respectively); insulin reached the point of maximal resistance, which is explained by a decrease of maximum specific insulin binding, %Bo (6.32+/-0.51) at minimal values due to a decrease of high-affinity receptor number per erythrocyte, N-AA (16+/-2) at minimal values. Moreover, the negative correlation between progesterone (31.2+/-0.2 ng/mL) and Ka-AA (r=-0.71) could possibly be related to this maximal resistance.

Linkage of the human inducible nitric oxide synthase gene to type 1 diabetes.

Exposure of human pancreatic islets to a mixture of cytokines induces expression of the inducible nitric oxide synthase (iNOS), impairs beta-cell function, and induces apoptosis. We performed a mutational scanning of all 27 exons of the human NOS2 gene and linkage transmission disequilibrium testing of identified NOS2 polymorphisms in a Danish nationwide type 1 diabetes mellitus (IDDM) family collection. Mutational screening was performed using PCR-amplified exons, followed by single stranded conformation polymorphism and verification of potential polymorphisms by sequencing. The transmission disequilibrium test was performed in an IDDM family material comprising 257 Danish families; 154 families were affected sibling pair families, and 103 families were simplex families. In total, 10 polymorphisms were identified in 8 exons, of which 4 were tested in the family material. A C/T single nucleotide polymorphism in exon 16 resulting in an amino acid substitution, Ser(608)Leu, showed linkage to IDDM in human leukocyte antigen DR3/4-positive affected offspring (P = 0.008; corrected P = 0.024). No other distorted transmission patterns were found for any other tested single nucleotide polymorphism or constructed haplotypes with the exception of those including data from exon 16. In conclusion, linkage of the human NOS2 gene to IDDM in a subset of patients supports a pathogenic role of nitric oxide in human IDDM.

[Hematic parameters in chronic hypoxemia]. / Parámetros hemáticos en hipoxemia crónica.

The hematic effects of hypoxia have been studied in 184 patients divided in four groups: 1) 10 patients with pO2 values in capillary blood lower than 43 mmHg; 2) 40 patients with pO2 between 43 and 50 mmHg; 3) 134 subjects with pO2 between 51 and 62 mmHg; and 4) 39 normal subjects (control). Hypoxemic subjects show higher erythrocyte concentrations than normoxemic ones, but without reaching the point of polycythemia and without significant differences in the hemoglobin concentration. The values of the mean corpuscular volume, the mean corpuscular hemoglobin and the concentration of the mean corpuscular hemoglobin show no significant differences between the groups. The amplitude of the red corpuscle distribution has not shown statistically significant differences between the groups of more pronounced hypoxia and those of slight hypoxia and control. The hematocrit, determined in the autoanalyzer, does not show any significant differences between the groups, whereas the one obtained by centrifugation is higher in the hypoxemic groups. Differences are non-significant in platelet count, mean platelet volume, and platelet distribution among the groups. The leucocyte count yields progressively higher values as blood pO2 decreases, with an accompanying increase in the percentage of neutrophyle granulocytes and a decrease in lymphocytes. Leucocytes with peroxidasic activity are significantly higher when the oxygen offer is lower.

[Differences of males and females regarding the binding capacity of insulin to erythrocyte receptors]. / Diferencias entre varones y mujeres en la capacidad de ligado de la insulina a los receptores eritrocitarios.

The analysis of insulin receptors in erythrocytes demands a relatively small blood sample, which justifies the interest in its use as an index of the cellular capacity for binding hormone. In order to establish criteria for normalcy, the capacity of erythrocytes for binding in vitro insulin labelled with 125I before increasing concentrations of cold insulin (from 0.5 to 10(3) ng/ml), was studied in a group of 41 healthy men and another of 35 women with normal menstrual cycles. In the female group the study was carried out in three different days of the same cycle (days 3, 12 and 21). The binding capacity in the male was higher than in the female (p less than 0.05) in the follicular phase (days 3 and 12) as well as in the luteal phase (day 21) and, among women, it was higher in the follicular phase than in the luteal one (p less than 0.05). The results indicate that progesterone, as well as prolactin and glucagon, may play an important role in the binding capacity of insulin to its receptor. To make the values comparable, it is suggested that blood extraction in women be carried out during the first five days of the cycle.