Evaluation of age-related changes of physicochemical properties and functional activity of rat adipose plasma membranes and their possible relationship.

Studies were carried out to evaluate structural state of adipose plasma membranes (PM) from mature adult and aged Wistar rats and its possible relation to functional changes in aging. PM lipids were probed by fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH) and pyrene. The data on DPH anisotropy, pyrene excimerization and induction resonance energy transfer (IRET) from PM proteins to pyrene provided the evidence for age-dependent decrease in PM lipid phase fluidity inclusive of that of annular lipid. Interaction between PM lipids and integral proteins also changed in aging. The observed structural changes were due to age-related lipid compositional modification. Evidence for this conclusion was provided by the following data: (i) DPH anisotropy was increased in aging both in PM and liposomes from the same PM lipids; (ii) both saturation/unsaturation fatty acid ratio and relative content of phosphatidylethanolamine (PE) increased in aged PM, whereas cholesterol/phospholipid and lipid/protein ratios were age-independent; (iii) PM polypeptide composition remained practically unchanged during aging. Age-related changes of the PM structure were accompanied by a twofold decrease of high affinity insulin binding sites and elevation of their affinity to insulin. It was suggested that age-related changes of physicochemical properties of PM lipid phase might affect protein molecular conformation and function through either changes in bulk lipid fluidity or through specific lipid-protein interactions.

Alteration of 5'-nucleotidase properties in rat adipose and liver plasma membranes after 1 Gy whole-body gamma-irradiation.

5'-Nucleotidase activities in rat adipose and liver plasma membranes (PM) were examined at various times after 1 Gy whole-body gamma-irradiation. Changes in the enzyme kinetic parameters were recorded 6 and 14 weeks after exposure: Km decreased while Vmax increased. The enzyme in control PM showed temperature-dependent Arrhenius plots with a lower activation energy at temperatures above a break point at approximately 28 degrees C, whereas 5'-nucleotidase in irradiated PM showed a constant activation energy between 10 and 40 degrees C which was reasonably close to the value observed controls at temperatures below the break point. Furthermore, the interaction of [3H]-AMP with the 5'-nucleotidase catalytic site was studied on adipose PM using a rapid filtration technique. gamma-Irradiation was associated with an increased number of specific AMP-binding sites and decreased ligand affinity. Comparison of the presented data with previous work (Yegutkin et al. 1993a,b) indicate significant functional and structural modification of rat adipose and liver PM following 1 Gy gamma-irradiation and reveals interrelation of these changes.

[Elevation of serum glucose concentration after administration of 5'-AMP to rats and modulation of this process dynamics following single gamma-irradiation at 1 Gy dose]. / Povyshenie kontsentratsii gliukozy v krovi krys posle vvedeniia 5'-AMP i izmeneniie dinamiki étogo protsessa pod deistviem odnokratnogo gamma-oblucheniia v doze 1 Gr.

Injection of exogenic 5'-AMP to rats was accompanied by pronounced and transient adenosinemediated elevation of serum glucose concentration. Both efficiency and duration of the observed hyperglycemic effect were increased within the first week after single whole-body gamma-irradiation (137Cs) of the animals at 1 Gy dose. These data suggest modification of purinergic regulation of some processes of carbohydrate metabolism and disturbance of the organism tolerance towards the glucose following 1 Gy gamma-irradiation.

[Down regulation of insulin receptors in the rat liver in aging]. / Down-reguliatsiia insulinovykh retseptorov v pecheni krys pri starenii.

No decrease in the specific binding of 125I-insulin in the liver plasmatic membranes in response to insulin administration (2 units per 100 g/w) occurred in 24-26 month old rats whereas the response was obvious in 5-6 month old animals. The older animals showed a less obvious response of insulin receptors to 2-week administration of the hormone.

[Structural and functional changes in plasma membranes of rat adipose tissue after chronic gamma-irradiation at a dose of 1 Gy]. / Strukturno-funktsional'nye izmeneniia plazmaticheskikh membran zhirovoi tkani krys plase khronicheskogo gamma-oblucheniia v doze 1 Gr.

The structural (microviscosity, lipid-protein interactions, lipid composition) and functional (5'-nucleotidase properties) status of rat adipose plasma membranes was studied 4, 10 and 30 days after prolonged gamma-irradiation at 1 Gy dose (period of exposure 94 days). The relative content of unsaturated fatty acids of the membrane phospholipids from irradiated rats was decreased during the period under study, whereas cholesterol/phospholipid molar ratio and pyrene excimerization parameter remained unchanged. Efficiency of the inductive-resonance energy transfer from the membrane tryptophenyls to pyrene was raised at 10 days postirradiation indicative on the lipid-protein alterations within membrane matrix, gamma-irradiation was characterized by the following features of 5'-nucleotidase; (1) two-fold increasing of Michaelis constant Km and (2) raising by 3-4 degrees C of the breakpoint on the enzyme Arrhenius plot. Scatchard parameters of 3H-AMP binding to the irradiated plasma membranes (measured by rapid filtration technique) were not different from the control ones.

[Kinetic properties of 5'-nucleotidase in the adipose tissue, liver and blood of rats of different ages]. / Kineticheskie svoistva 5'-nukleotidazy v zhirovoi tkani, pecheni i krovi krys raznogo vozrasta.

The kinetic characteristics (Vmax and Km) of membrane-bound and serum 5'-nucleotidases from rats of different age groups are studied. The age-related increase of Km parameter in plasma membranes of fatty tissue and liver demonstrated a lower enzyme affinity to the substrate in ageing membranes. The specific activity of 5'-nucleotidase in blood serum of aged animals was below that in young ones, while Km value remained stable. Tissue differentiation of the catalytic properties of the enzyme and their aged-related characteristics may be to a considerable extent determined by the physicochemical state of cell membranes.

[Age-dependent characteristics of the effect of insulin on 5'-nucleotidase activity in liver plasma membranes]. / Vozrastnye osobennosti vliianiia insulina na aktivnost' 5'-nukleotidazy v plazmaticheskikh membranakh pecheni.

Vmax of 5'-nucleotidase was found to be similar in liver plasmatic membranes of both 4-5 months old male rats and 24-26 months old animals. At the same time, Km value was higher in the membranes of old rats than in young animals. Insulin (administered at a dose of 2 un per 100 g of body mass) increased the enzyme Vmax without some age-dependent differences and decreased Km value in old animals as compared with controls.

[A modified method of isolation of Langerhans islets from the rat pancreas]. / Modifikatsiia metoda vydeleniia ostrovkov Langergansa iz podzheludochnoi zhelezy krys.

A simple procedure is developed for isolation of Langerhans islands (LI) from rat pancreas. Homogenization of pancreatic tissue was carried out using two "Record" syringes equipped with needles of various diameter. Collagenase was not used in the procedure. After homogenization LI were individually separated using stereomicroscope. The insulin-producing capacity of LI was estimated by assay of immunoreactive insulin content in LI and in the incubation media at 0 degrees and 37 degrees as well as by their reaction to various concentrations of glucose. The procedure enabled to isolate functionally active LI and to study biosynthesis and secretion of insulin in vitro.

[Age-related characteristics of insulin regulation of the physico-chemical properties of liver membranes]. / Vozrastnye osobennosti reguliatsii insulinom fiziko-khimicheskikh svoistv membran pecheni.

Alterations in physico-chemical properties of rat liver plasmatic membranes induced by insulin were shown to be age-dependent The experiments showed also that high doses of the hormone impaired distinctly the membranes in old animals. The relationship between structural alterations in plasmatic membranes and the rate of lipid peroxidation was observed.

[Effect of starvation on lipid peroxidation and fatty acid composition in the blood of young and old rats]. / Vliianie golodaniia na perekisnoe okislenie lipidov i zhirnokislotnyi sostav syvorotki krovi u molodykh i starykh krys.

After starvation during 48 hrs there was no alteration in blood serum of young rats (4-5 months old) in content of malonic dialdehyde but it was decreased in the old animals (24-26 months old). At the same time, the fatty acid composition of blood serum similarly altered in the both experimental groups. There was an increase in content of saturated fatty acids and a decrease in content of unsaturated fatty acids. Total amount of free fatty acids was increased in young starved rats and unaltered in old animals. Effect of starvation on the body antioxidant system is discussed.

[Prostaglandins E and lipolysis in adipose tissue of normal and starved rats during aging]. / Prostaglandiny gruppy E i lipoliz v zhirovoi tkani intaktnykh i golodavshikh krys pri starenii.

Basal rate of lipolysis and content of prostaglandins E were similar in epididimal adipose tissue of both 5-6 months and 24-26 months old male rats, i. e. these patterns were not altered with age. Starvation during 24 and 48 hrs was accompanied by activation of lipolysis in young rats and by its inhibition in old animals. After the starvation content of prostaglandins E was increased in adipose tissue of young rats. The increase was especially distinct within 48 hrs; in the group of old rats content of prostaglandins E in adipose tissue was markedly decreased as compared with young animals.

[Various indices of lipid metabolism in patients with gastroduodenal pathology]. / Nekotorye pokazateli lipidnogo obmena u bol'nykh s gastroduodenal'noi patologiei.

Lipid metabolism was studied in patients with impairments of gastroduodenal tract before and after treatment. The data obtained suggest that the treatment of these patients should involve both antioxidants and angioprotective drugs in order to prevent vascular deteriorations.

[Diagnosis and prevention of diabetic angiopathies]. / Diagnostika i profilaktika diabeticheskoi angiopatii.

The paper presents a new method to diagnose the I preclinical stage of diabetic angiopathy permitting identification of the risk groups and design of preventive measures. The method implies evaluation of the biochemical index characterizing serum lipids structural defense against lipid peroxidation.

[Age and features of insulin reception by the plasma membranes of liver cells]. / Vozrastnye osobennosti retseptsii insulina plazmaticheskimi membranami kletok pecheni.

The specific binding of 125I-insulin by liver cell plasmatic membranes of rats aged 5-6 mos. and 24-26 mos. was studied. A decrease in hormone binding with the receptors of old animals as compared to young ones in the presence of similar concentration of immunoreactive insulin in the blood was established. A graphical analysis of the data after Scatchard showed that an age-related decrease in 125I-insulin binding with rat liver cell plasmatic membranes resulted from the loss of binding sites in old rats as compared to young animals. The affinity of insulin receptors to the hormone did not change with age.

[Insulin-inducible structural reorganizations in the lipid bilayer of fatty tissue plasma membranes and their age-related characteristics]. / Indutsiruemye insulinom strukturnye perestroiki lipidnogo bisloia plazmaticheskikh membran zhirovoi tkani i ikh vozrastnye osobennosti.

Effect of insulin on properties of plasmatic membranes (PM) from adipose tissue of young and aged rats has been studied. Insulin increased the anisotropy of PM. The data obtained indicate that this effect of insulin was specific and was confined to specific domains of the membrane matrix. Both the level of insulin-induced structural changes in PM and fluidity of lipid bilayer decreased with age.

[Age-specific characteristics of the effect of various hormones on the lipolysis in the adipose tissue of rats under normal conditions and in starvation]. / Vozrastnye osobennosti vliianiia nekotorykh gormonov na lipoliz v zhirovoi tkani krys v norme i pri golodanii

Experiments were conducted in vitro; a study was mode of the age peculiarities attending be invluence of adrenaline, ACTH, STH on the lypolysis in the adipose tissue of rats under normal conditions and in starvation. During the process of ageing there occurs no change in the adipose tissue sensitivity to the action of hormones stimulating the lipolysis, but the capacity to react to high hormone doses is decreased. Elevation of the basal lypolysis in the adipose tissue of young rats occurs during starvation; the lypolytic action of the hormones falls. Starvation fails to alter the basal lypolysis in the adipose tissue to react to the hormone action.

[Effect of age and body weight on the insulin, glucagon and somatotropin content of the human blood]. / Vliianie vozrasta i massy tela na soderzhanie insulina, gliukagona i somatotropina v krovi cheloveka.

Insulin, glucagon and somatotropin content in the blood of men and women with the normal and excess body weight was investigated by means of radioimmunoassay. The age of the persons under study ranged from 20 to 99 years old. It has been established that insulin and somatotropin concentration remains unchanged and that of glucagon increases with aging. When the body weight is excessive the blood insulin and glucagon levels rise, whereas that of somatotropin lowers. The differences between glucagon and somatotropin concentrations in persons with the normal and excessive body weight disappear with aging.