Transient ischemic alteration of synaptosomal neutral acid uptake

Summary The effect of cerebral ischemia and postischemia on the synaptosomal uptake of some neutral amino acids was determined in mongolian gerbils at various periods of time. A transiently increased uptake of³H isoleucine,¹⁴C cycloleucine and³H phenylalanine in the synaptosomes was found after 3 min of bilateral common carotid occlusion which returned to normal at 30 min of reestablished cerebral blood circulation.     

Einbauunterschiede in den Zellschichten des Cortex nach Markierung mitd,l-Prolin-H3 bei der Maus

Summary Autoradiographic studies of the mouse brain following incorporation ofd,l-proline-H³ andl-histidine-H³ show a wide variation of the regional uptake ofd,l-proline into the cerebral nerve cells, in contrast tol-histidine. In the cerebral cortex proline is to be found only in the nerve cells of the lamina ganglionaris (V) and lamina multiformis/infima (VI/VII). Subsequent translocation of radioactivity is indicative of an axoplasmic flow of proline-labelled substances into the distal parts of the neuronal processes.

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Mit dankenswerter Unterstützung durch das Landesamt für Forschung Nordrhein-Westfalen.     

Uptake of3H-GABA (γ-aminobutyric acid) and3H-leucine in the pancreatic islets and substantia nigra of the rat

Summary Isolated pancreatic islets and thin slices of substantia nigra (SN) of the rat were incubated in a medium containing³H-GABA or³H-leucine to test the activity of both tissues in the uptake of those substances. Pancreatic islets showed a low uptake of both³H-GABA and³H-leucine, but SN had a high activity in the uptake of³H-GABA, though not for³H-leucine. This suggests that GABA contained at high levels in the pancreatic islets plays some functional role other than in neurotransmission as in the central nervous system (CNS).     

Dual modes of 5-(N-ethyl-N-isopropyl)amiloride modulation of apical dipeptide uptake in the human small intestinal epithelial cell line Caco-2

Selective pharmacological Na⁺/H⁺ exchange (NHE) inhibitors were used to identify functional NHE isoforms in human small intestinal enterocytes (Caco-2) and to distinguish between direct and indirect effects on transport via the intestinal di/tripeptide transporter hPepT1. The relative potencies of these inhibitors to inhibit ²²Na⁺ influx identifies NHE3 and NHE1 as the apical and basolateral NHE isoforms. The Na⁺-dependent (NHE3-sensitive) component of apical dipeptide ([¹⁴C] Gly-Sar) uptake was inhibited by the selective NHE inhibitors with the same order of potency observed for inhibition of apical ²²Na⁺ uptake. However, 5-(N-ethyl-N-isopropyl) amiloride (EIPA) also reduced [¹⁴C]Gly-Sar uptake in the absence of Na⁺ and this inhibition was concentration and pH (maximal at pH 5.5) dependent. NHE3 inhibition by S1611 and S3226 modulates dipeptide uptake indirectly by reducing the transapical driving force (H⁺ electrochemical gradient). EIPA (at 100 μM) has similar effects, but at higher concentrations (>200 μM) also has direct inhibitory effects on hPepT1.Received 28 February 2005; received after revision 20 April 2005; accepted 20 May 2005     

Über den Einfluss einiger oberflächenaktiver Substanzen auf den Einbau freier Fettsäuren in die Lipoide des Rattenpankreas in vitro

Summary Non-ionic surfactants showed minor effects on the uptake of H³-palmitic acid into the lipids of rat pancreasin vitro. In the presence of the cationic and anionic surfactants tested, the fraction of free H³-palmitic acid bound by the tissue increased. Only the anionic laurylsulfate, however, stimulated the uptake of H³-palmitic acid into neutral lipids without stimulating its uptake into phospholipids.      

Über die Wirkung blutzuckersenkender Sulfonylharnstoffe auf das isolierte Rattenzwerchfell

Summary The action of blood sugar depressing sulfonylureas on glucose and oxygen uptake, as well as on glycogen content and formation of C¹⁴O₂ from uniformly labelled C¹⁴-glucose was investigated in rat hemidiaphragms incubated in phosphate buffer. The following results were obtained: (1) Tolbutamide and Carbutamide increased the glucose uptake. (2) Tolbutamide decreased the glycogen-content. (3) Oxygen uptake as well as formation of C¹⁴O₂ were increased by Tolbutamide. (4) The action of Tolbutamide and insuline was equal with respect to glucose uptake but different as regarding the glycogen content, oxygen uptake and CO₂-formation.It is concluded that sulfonylureas increase glucose oxidation in the rat hemidiaphragm probably without increasing insulin sensitivity. To our knowledge this mechanism of action has hitherto not been described.     

Synaptic development in brains of rats exposed perinatally to ethanol

Summary Development of brain synaptosomal uptakes of³H-norepinephrine and³H-dopamine in pups whose mothers received ethanol were nearly normal. However, development of synaptosomal uptake of³H-serotonin was significantly lower than in controls, while uptake of³H-norepinephrine into synaptic storage vesicles was increased.The authors thank F.J. Seidler and W.L. Whitmore for their technical assistance. Research was supported by U.S. Public Health Service grants AA-02935 and DA-00465. TAS is recipient of Research Scientist Development Award DA-00006 from the National Institute on Drug Abuse, and SMS is recipient of Research Scientist Award MH-06489 from the National Institute of Mental Health.     

High and low affinity transport ofL-arginine in rat brain synaptosomes

The uptake ofL-arginine into purified rat brain synaptosomes was investigated with respect to time and various concentrations ofL-[³H] arginine. Specific uptake was found to be linear with time for up to 5 min of incubation at 37°C. Electrolytes, including sodium chloride, potassium chloride, magnesium chloride and calcium chloride, inhibited uptake of 3 ML-arginine, and the inhibitory effect increased with increased electrolyte concentration under constant osmolarity. It was found thatL-arginine was transported into synaptosomes by two uptake components — a high affinity component (3.5 M) and a low affinity component (100 M). These two components were similar to the Ly⁺ system because of their extreme sensitivity to inhibition byL-lysine andL-ornithine but were distinguishable from each other by kinetic analysis of the uptake data and by their relative sensitivity to inhibition by several amino acids.     

Impaired insulin release in aging rats: Metabolic and ionic events

We investigated the effect of aging on glucose uptake, glucose-induced O₂ consumption, glucose-induced⁴⁵Ca movements, and calmodulin content to elucidate age-related impairment of glucose-induced insulin release in pancreatic islets of Wistar rats. Intact pancreatic islets from old (24-month-old) rats showed impaired glucose-induced insulin release; glucose uptake and O₂ consumption were lower in old than in young (2-month-old) or adult (12-month-old) rats. Moreover,⁴⁵Ca uptake and calmodulin content were decreased in pancreatic islets from older rats, which explained the impairment in glucose-induced insulin release in aging. No major differences between the 3 age groups in glucose-induced⁴⁵Ca efflux in pancreatic islets were observed.     

Phagocytose des liposomes par les macrophages péritonéaux de souris

Summary Uptake of¹⁴C-cholesterol or³H-cholesterol labelled liposomes, stimulation of¹⁴C-glucose oxidation, as well as ultrastructural and autoradiographical experiments have shown that liposomes are phagocytized by mouse peritoneal macrophages. Further results have shown that degradation of liposomes was not complete 2 h after uptake.     

The effect of bovine myelin basic protein on uptake and release of H3-labelled 5-hydroxytryptamine,L-noradrenalin and γ-aminobutyric acid in rat cortex slices

Summary At concentrations above 10^–5 M myelin basic protein (MBP) induced a small inhibition of the uptake of H³-5HT and H³-NA into rat cortex slices. Release of 5HT, NA and Gaba was not affected by 10^–5 M MBP.Acknowledgment. The authors wish to thank W. Bucher for the preparation of MBP.     

Effect of the growth-promoting alpha-globulin (GPAG) on in vitro incorporation of exogenous DNA into mammalian cells

Summary The uptake of exogenous³H-DNA by mammalian cells is increased in the presence of a specific serum protein complex — growth-promoting alpha-globulin (GPAG).³H-DNA is retained in the cell nucleus in a quantity 3 times higher than for control cultures without GPAG even after 47h of additional cultivation in the medium without³H-DNA.     

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     

Irradiation of the head by60Co opens the blood-brain barrier for drugs in rats

Summary The passage of 6 model drugs; acetylsalicylic acid, chloramphenicol, ethimizol, carbisocaine, heptacaine, and diazepam, through the blood-brain barrier, was determined in unirradiated control rats and in animals 1, 3, and 7 days after irradiation of the head only with a dose of 25 Gy from a⁶⁰Co source. The brain uptake index (BUI), which compares the uptake of the test substance with that of³H₂O 5 s after their injection into the common carotid artery, was significantly increased in comparison with unirradiated controls 7 days after irradiation, for all substances tested except for ethimizol. For acetylsalicylic acid and chloramphenicol it was also significantly increased in the other time intervals. The less lipophilic substances showed a greater relative increase of BUI than the more lipophilic ones.     

Experiments on the mechanism of the inhibition of mitochondrial Ca2+ transport by La3+ and ruthenium red

Summary The effects of La³⁺ and ruthenium red on the energy-linked uptake of Ca²⁺ mediated by a synthetic neutral Ca²⁺ ionophore have been investigated in rat liver mitochondria. The results indicate that unspecific surface charge effects do not play a major role in the mechanism of inhibition of mitochondrial Ca²⁺ transport by La³⁺ and ruthenium red.Acknowledgments. The authors are indebted to Prof. W. Simon, ETH Zurich, for having provided samples of the synthetic neutral Ca²⁺ ligand, and to M. Mattenberger for the valuable technical assistence. The work was supported by a grant of the Swiss Nationalfonds (grant No. 3.1720.75).     

The sequential uptake of (14C) deoxyglucose in brain after embolic stroke

Summary An i.v. bolus of (¹⁴C) deoxyglucose was injected into 4 groups of rats which simultaneously were embolized through the internal carotid artery. 15 and 30 min post embolization there was a massive decrease in (¹⁴C) deoxyglucose uptake in both deep and cortical structures. At 4 h a small zone of increased (¹⁴C) deoxyglucose uptake persisted around each embolized microsphere.     

Cellular and subcellular localization of3H-diethylstilbestrol in the pituitary,oviduct and uterus of the female rat

Summary Female rats were injected with³H-diethylstilbestrol. The pituitaries, oviducts, and uteri were removed and processed for autoradiography. The nuclear uptake and retention in these tissues appeared similar to that seen after the injection of³H-estradiol except in the pars nervosa of the pituitary gland.This study was supported by US PHS Career Development Award No. NS00164 and PHS Grant No. NS21933.     

Influence of hypoxia on contractility and calcium uptake in rabbit aorta

Summary The influence of hypoxia on noradrenaline (NA)-induced contractions and⁴⁵Ca uptake has been studied on isolated rabbit aortae. Hypoxia significantly decreased the contractility of aortic strips. NA stimulation resulted in increased or decreased⁴⁵Ca uptake by normoxic or hypoxic specimens, respectively. Relating⁴⁵Ca movement with mechanical activity, the results suggest that decrease in Ca⁺⁺ uptake may be mechanism for hypoxic relaxation of aortic smooth muscle.The author acknowledges facilities at the Wellcome Surgical Research Institute, University of Glasgow, U.K. Much of this work was in collaboration with Drs Sheila Jennett and J.D. Pickard.     

Bicarbonate and chloride transport across rat ileal basolateral membrane

The mechanisms of HCO ₃ ^– and Cl^– transport across basolateral membranes from rat ileum were investigated in isolated vesicles by means of uptake experiments. Neither Cl^–/HCO ₃ ^– exchanger nor Na⁺–(HCO ₃ ^– )_n cotransport seem to be present in ileal basolateral membranes. Moreover Cl^– uptake is unaffected bycis Na⁺ and/or K⁺ gradients, indicating the absence of Na⁺–Cl^–, K⁺–Cl^– and Na⁺–K⁺–2Cl^– symport activity. An electrically conductive pathway seems to be responsible for both HCO ₃ ^– and Cl^– fluxes. Evidence is also given for the presence of a Na⁺/H⁺ exchanger at the basolateral pole of ileal enterocytes.     

Influence of progesterone on protein and RNA synthesis in cultured chick embryo liver cells

Summary Chick embryo liver primary cultures, when added with progesterone, exhibit, in comparison with the controls, a normal growth, a decline of both³H-uridine uptake and incorporation into total RNA, a decline of³H-leucine and¹⁴C serine incorporation into the proteins. Progesterone is not able to stimulate phosvitin synthesis induction.These studies were supported in part by the Italian CNR grants.