Carotid back pressure following bilateral carotid occlusion in normotensive and spontaneously hypertensive rats

Summary In SHR, CBP fell markedly and remained below 50 mm Hg after carotid occlusion despite SBP being elevated, while in NTR changes in CBP were related with changes in SBP. Vascular resistance of the brain in hypertensive rats is discussed.     

Dissociation of digoxin-like immunoreactivity and Na+,K+-ATPase inhibitory activity in rat plasma

We measured endogenous digitalis-like factor (EDF) in rat plasma during acute saline infusion by two different procedures. Na+,K+-ATPase inhibitory activity in the rat plasma significantly increased during saline loading (7.8 +/- 2.2 vs 2.5 +/- 0.9%, with and without acute saline loading, respectively, p less than 0.05). On the other hand, the plasma digoxin-like immunoreactivity significantly decreased during acute saline loading (16.9 +/- 1.6 vs 32.0 +/- 2.8 pg digoxin equivalents/ml, with and without acute saline loading, respectively, p less than 0.01). These results indicate that the major substances detected by digoxin-like immunoreactivity and direct Na+,K+-ATPase inhibitory activity are completely different, at least in rat plasma.     

Increase in Na+, K+ -ATPase enzyme units in liver and kidneys from essential fatty acid deficient rats.

(3H)-Ouabain binding to liver and kidney preparations was utilized to estimate the number of Na+, K+-ATPase enzyme units in livers and kidneys from rats fed 2% corn oil supplemented or fat-free diets. The specific (3H)-ouabain binding in liver and kidney preparations from fatty acid deficient rats was increased approximately 40%, but the affinity of the binding sites for ouabain (Kd-value) remained unchanged. The increased concentration of Na+, K+-ATPase enzyme units observed in the essential fatty acid deficient rats may contribute to the reduced body fat accumulation and elevated heat production observed in these animals.     

Lower limit of cerebral autoregulation in normotensive and spontaneously hypertensive rats

Summary Cerebral autoregulation was examined in NTR and SHR. The lower blood pressure limit of autoregulation being 95 mm Hg in SHR was shifted upwards from 62 mm Hg in NTR.     

The Na+, K+, Ca2+, Mg2+ and Cl− composition of giant fibers fromBalanus nubilus

Zusammenfassung Es werden Analysenresultate über den Ionengehalt von einzelnen Muskelfasern der Entenmuschel,Balanus nubilus, mitgeteilt. Es wurden Unterschiede nachgewiesen in der Ionenkonzentration verschiedener Fasern, die von demselben Muskelbündel isoliert worden waren.     

Isoprotenerol induction of pineal serotonin N-acetyltransferase in normotensive and spontaneously hypertensive rats

Zusammenfassung Verabreichung von Isoprotenerol, eines -adrenergen Agonisten, induziert einen signifikant höheren Anstieg der Aktivität der Serotonin-N-Acetyltransferase in der Epiphyse von spontan hypertensiven, im Vergleich mit normotensiven, Rattenmännchen. Derselbe Unterschied wurde auch bei Weibchen beobachtet, jedoch liegen die Aktivitätswerte bei spontan hypertensiven Männchen allgemein höher. Die durch Isoprotenerol erhöhte Induktion der Serotonin-N-Acetyltransferase erzeugt hinsichtlich der Catecholamine in den Pinealozyten von spontan hypertensiven Ratten eine veränderte Reaktivität der Achse -Rezeptor-Adenylzyklasesystem-Serotonin-N-Acetyl transferase.     

Increased Na+-H+ exchanger activity in the ileal brush-border membrane of spontaneously hypertensive rats

In the present study, we have examined the intestinal Na⁺ transport, through the Na⁺-H⁺ exchanger, in ileal brush-border membrane vesicles (BBMV) isolated from spontaneously hypertensive rats (SHR), and normotensive Wistar Kyoto (WKY) rats as a control group. Na⁺ uptake into ileal BBMV was stimulated in the presence of a proton gradient (pH 5.5 inside/pH 7.5 outside) in SHR and WKY rats, resulting in a transient accumulation (overshoot) in both groups of rats. No overshoot was observed in the absence of a pH gradient. The magnitude of the accumulation was significantly higher in SHR than in WKY rats. Uptake of Na⁺ at equilibrium was identical in the presence and the absence of a proton gradient and was not changed in SHR. The use of amiloride inhibited pH gradient-driven Na⁺ uptake in a dose-dependent manner with a Ki of 90 μM and 100 μM for SHR and WKY rats, respectively. The relationship between proton gradient-driven Na⁺ uptake and external Na⁺ concentration was saturable and conformed to Michaelis-Menten kinetics in both SHR and WKY rats. Lineweaver-Burk analysis of the pH gradient-driven Na⁺ uptake indicated values of V_max that were significantly increased in SHR compared to WKY rats (11.4±0.55 nmol/mg/8 s vs. 4.96±0.78 nmol/mg/8 s for SHR and WKY rats, respectively). In contrast, similar K_m values for Na⁺ were found between SHR and WKY rats (4.0±0.2 mM vs. 4.9±0.6 mM for SHR and WKY rats, respectively). These studies show derangement in ileal BBMV Na⁺ transport of SHR, which is characterized by increased Na⁺-H⁺ exchanger activity. Received 18 December 1996; received after revision 3 February 1997; accepted 7 February 1997     

Intravital measurement of arteriolar pressure and tangential wall stress in normotensive and spontaneously hypertensive rats (established hypertension)

Summary Under intravital conditions, intravascular pressures of mesenteric resistance vessels were measured in normotensive (NR, mean blood pressure 92 mm Hg) and spontaneously hypertensive rats (SHR, 161 mm Hg) being elevated over all by about 75%; the tangential wall stress (=p·r/h; p represents the intravascular pressure and r/h the ratio of internal radius to wall thickness) was found to be increased by 120–140% in SHR.Supported by the DFG.     

Dissociation between compensatory renal growth and induction of (Na++K+-ATPase in rat kidney after uninefrectomy

Zusammenfassung Nach Uninephrektomie und bilateraler Adrenalektomie entsteht eine Dissoziation zwischen der Nierenvergrösserung und der (Na⁺+K⁺)-ATPase Aktivität. Es besteht wahrscheinlich kein Zusammenhang zwischen der Nierenvergrösserung und der Induktion von (Na⁺+K⁺)-ATPase. Auch in der vergrösserten Niere sind die Nebennierenhormone notwendig, um die (Na⁺+K⁺)-ATPase zu erhalten.

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The work was supported by a grant from P. Carl Petersen's Fund. Mrs.Birthe Bagge Hansen provided excellent technical assistance.     

Effect of various stressors on the levels of lipid peroxide,antioxidants and Na+, K+-ATPase actrivity in rat brain

The level of malondialdehyde (MDA), an index of lipid peroxidation, and the antioxidants superoxide dismutase (SOD) and glutathione (GSH), as well as the activity of Na⁺, K⁺-ATPase, were assessed in whole rat brain after immobilization, anemic hypoxia (NaNO₂) and 72 h starvation. The effect of these stressors on plasma glucose and corticosterone levels was also observed. Hypoxia and starvation stimulated the lipidj peroxide formation in braini as indicated by an increase in the level of MDA, being higher after starvation than hypoxia. Brain SOD activity was also increased in response to hypoxia and starvation while GSH content was only diminished ini hypoxia. However, neither MDA nor antioxidants were affected by immobilization. On the other hand, the activity of brain Na⁺, K⁺-ATPase was significantly increased by immobilization and hypoxia but decreased in starvation. A similar pattern of change was also observed in plasma glucose and corticosterone levels in response to these stressors. These results elucidate differences in the biochemical response of animals towards various types of stress, with increased lipid peroxide formation in hypoxia and starvation.     

Effect of mycotoxin (T-2 toxin) on catecholamine and Na+, K+-ATPase levels in rat epididymis

Summary The effect of mycotoxin (T-2 toxin) on catecholamines and Na⁺, K⁺-ATPase activities in rat epididymis has been evaluated. Dopamine and norepinephrine levels were significantly elevated in the caput and corpus regions whereas their levels remained unchanged in the caudal part of the epididymis. Na⁺, K⁺-ATPase activity was significantly increased in all the three regions of rat epididymis as a result of the toxin treatment. These changes may suggest an adverse effect on epididymal functions in rats.     

Effect of mycotoxin (T-2 toxin) on catecholamine and Na+, K+-ATPase levels in rat epididymis

The effect of mycotoxin (T-2 toxin) on catecholamines and Na+, K+-ATPase activities in rat epididymis has been evaluated. Dopamine and norepinephrine levels were significantly elevated in the caput and corpus regions whereas their levels remained unchanged in the caudal part of the epididymis. Na+, K+-ATPase activity was significantly increased in all the three regions of rat epididymis as a result of the toxin treatment. These changes may suggest an adverse effect on epididymal functions in rats.     

Blood pressure and impairment of endothelium-dependent relaxation in spontaneously hypertensive rats

Correlation between hypertension and impairment of endothelium-dependent relaxation was demonstrated using aortae from certain strains of rats with various levels of spontaneous hypertension. It was also observed that the impairment of endothelium-dependent relaxation is the secondary change due to hypertension, and the level and duration of hypertension is the determinant factor of the impairment.     

Blood pressure and impairment of endothelium-dependent relaxation in spontaneously hypertensive rats

Summary Correlation between hypertension and impairment of endothelium-dependent relaxation was demonstrated using aortae from certain strains of rats with various levels of spontaneous hypertension. It was also observed that the impairment of endothelium-dependent relaxation is the secondary change due to hypertension, and the level and duration of hypertension is the determinant factor of the impairment.     

Evidence against a role of (Na++K+-ATPase in the alpha-adrenoceptor mediated positive inotropic effect of phenylephrine

Summary Phenylephrine (0.1–100 M) in the presence of 1 M propranolol increased the force of contraction in electrically driven papillary muscles from cats. This presumably alpha-adrenoceptor mediated positive inotropic effect of phenylephrine occurred without any influence on (Na⁺+K⁺-ATPase activity.This work was supported by the Deutsche Forschungsgemeinschaft.     

Changes in adenylate cyclase and 5-nucleotidase activities in liver membranes from alloxan diabetic rats

Liver membrane adenylate cyclase activity was significantly higher and 5'-nucleotidase activity significantly lower in alloxan diabetic rats compared with normal rats.