Biomedical subjects
Publications and source records attributed to Y V Postnov.
Both acetylcholine and eserine affect Ca2+-binding to mammalian erythrocyte membranes. Differences in Ca2+-binding between normotensive and hypertensive groups (human as well as rats) was found under eserine influence.
The in vitro study of the kinetics of 45Ca efflux from adipose tissue of rats reveals 3 pools of exchangeable calcium. Calcium content in the intracellular pools of adipose tissue of spontaneously hypertensive rats is increased as compared to that in normotensive controls.
Rats with renal and spontaneous hypertension do no differ from control normotensive rats in 14C-glucose uptake and triglyceride synthesis by the adipose tissue in vitro, both with and without insulin stimulation. Adrenalectomy (which eliminates the stabilizing effect of the corticosteroid hormones on the adipocyte membrane) reveals the differences between the hypertensive and normotensive rats in the response of the adipose tissue to insulin. While the adrenalectomized control rats show a significantly lowered "sensitivity" of the adipocytes to insulin, the adrenalectomized hypertensive rats do not reveal a noticeable change in glucose uptake and triglyceride synthesis under insulin stimulation of glucose transport (the adipose tissue of hypertensive rats "doesn't notice" adrenalectomy). The data obtained may indicate changes in the properties of the adipocyte membranes of rats with chronic arterial hypertension and suggest the presence of an extensive alteration of the function of cell membranes in both types of hypertension.
Ca binding in the red blood cell (RBC) membrane of spontaneously hypertensive rats (SHR) and of patients with essential hypertension was studied. Under conditions of physiological concentration of free Ca in the incubation medium of RBC the outer part of the membrane binds 393 +/- 32 and 435 +/- 30 nmole of Ca per ml of RBC in rats and humans, respectively, without essential differences in the amount of Ca in hypertensive individuals as compared to the normotensive controls. The membrane of red blood cell ghosts (RBCgh) at concentrations of free Ca corresponding to its intracellular concentration binds 4.28 +/- 0.39 and 3.53 +/- 0.15 nmole of Ca per mg of protein of RBCgh in rats and humans, respectively. This part of membrane-bound Ca pool (most probably related to the inner part of the red blood cell membrane) is reduced by 48% in SHR and by 28% in patients with essential hypertension as compared to normotensive controls. It is suggested that the decrease of Ca binding ability of the RBC membrane in both types of hypertension studied may be a pattern of a more widespread cell membrane defect.
The increase of the content of triphosphoinositide in the erythrocyte membrane in rats with spontaneous and renal hypertension and decrease of phosphatidylinositol at spontaneous hypertension were revealed.
The convoluted proximal and straight distal tubules and the medullary collecting ducts in kidneys of rats with ischaemic renal hypertension and with genetic spontaneous hypertension were studied by means of electron microscopic morphometry. The volume of mitochondria, the area of their cristae, of the outer surface and of membranes of the intercellular labyrinth, and other ultrastructural characterisitcs were calculated. No significant differences were found in proximal tubules between experimental and control animals, although in the distal tubules in both experiments the coefficient characterizing the level of morphologic organization of mitochondria, which takes into account their basic morphometric parameters, was reduced in hypertensive animals as compared with the intact ones. The volume of mitochondria and the area of their cristae in collecting ducts, and also the area of membranes of the intercellular labyrinth were increased. Our results suggest that in hypertension the reabsorption of substances from the proximal tubules is essentially normal, that it is reduced at the beginning of the distal tubules but is intensified in the collecting ducts.
Explore the source record for details and available documents.
Electron microscopic studies have been carried out of the interstitial cells (IC) of the renal medulla in rats with Goldblatt hypertension. Analysis of variance has not revealed any differences in the number of droplets of "unclamped" kidney in the hypertensive rats as compared to the normotensive rats ("resistant" rats, rats with unilateral nephrectomy, and intact rats) at periods from 3 weeks to 1 year. The total volume of the droplets in the IC cytoplasm in hypertensive and intact animals also revealed no difference 3 weeks after the beginning of the experiment. A positive correlation has been found between the number of the droplets and their volume but the low value of the correlation coefficient (r = +0.28) suggests that the number of the droplets cannot be a reliable indicator of the variation of the amount (volume) of thelipid material contained in them. Since it is just the latter parameter that carries the most information for evaluating the content of the droplet material in the IC, preference should be given to calculating the droplet volume rather than counting the number of droplets. The IC in the animals of the experimental groups revealed hypertrophy and hyperlasia of the endoplasmic reticulum and the Golgi complex, which were especially marked at the earlier stages of the experiments.
A morphometric study of the pancreatic islets in young spontaneously hypertensive rats (SHR, Okamoto and Aoki Wistar strain) and in normotensive Wistar rats (NWR) of the same age revealed that the SHR (in prehypertensive and in early hypertensive stages) had a significantly smaller mass of islet tissue and that the number of islets in the SHR was reduced by half. The ratio between the total masses of the pancreatic islets for the NWR and the SHR at the prehypertensive and early hypertensive stages was found to be: 1:0.53:0.61, respectively. The mass of the islet tissue in the SHR was reduced at the expense of the beta-cell component of the islets. No morphologic differences were found in the acinous tissue, and the pancreas and body weights were the same in both experimental groups. The glucose tolerance test revealed reduced glucose utilization in the SHR, which may be due to a relative insufficiency of the insulin secretion by the islets upon rapid (i.v.) glucose lodaing. Reduced plasma insulin response to i.v. glucose loading and a reduced rate of insulin utilization were found in the SHR as compared with the NWR. The poor development of the beta-cell tissue may be attributed either to the specific effect of the enhanced catecholamine excretion or to a low insulin requirement of the cell tissue membranes (insulin targets) as a consequence of the membrane ion transport alteration in spontaneous hypertension.
1. Erythrocyte membrane permeability to sodium and potsssium ions was studied in 8-10 weeks spontaneously hypertensive rats (SHR, Kyoto/Wistar strain), normotensive Wistar and Sprague-Dawley rats. 2. The rate of 22Na efflux from the erythrocytes and the rate constant of Na/Na exchange were considerably greater in SHR than in normotensive Wistar and Sprague-Dawley rats. This difference remained the same in rats adrenalectomized 7 days before the experiment. The maximum difference in the constants was found when the sodium-potassium pump was blocked by ouabain. 3. The accumulation of 42K in the erythrocytes of SHR (the sodium-potassium pump being blocked) took place at a considerably slower rate, and the K+ wash-out into a potassium-free medium was faster than that in the normotensive Wistar and Sprague-Dawley rats. 4. These results indicate a higher permeability of the erythrocyte membrane of SHR for Na+ and K+, compared with normotensive Wistar and Sprague-dawley strains. It is suggested that this may reflect a more widespread cell-membrane defect, which could serve as a general cause for activating the mechanisms maintaining high blood pressure.