From the results obtained in perfused rat hearts, Frick and Lowenstein proposed that ecto-5'-nucleotidase catalyzes a vectorial reaction in which AMP hydrolysis is accompanied by transfer of adenosine across the cell membrane (Frick, G.P., and Lowenstein, J.M. (1978) J. Biol. Chem. 253, 1240-1244). We have examined by the use of perfused rat livers, the uptake mechanism of adenosine generated f...

Several recent electrophysiological studies have demonstrated that nicotinic agonists stimulate the release of gamma-aminobutyric acid (GABA) from rodent brain tissue. Our studies used a neurochemical approach to characterize nicotinic receptor-stimulated [3H]-GABA release from mouse brain synaptosomes. Nicotine increased [3H]-GABA release from synaptosomes preloaded with [3H]-GABA in a concent...

In order to develop more selective methods for labeling brain dopamine receptors, this study describes in detail the properties of 2-amino-6,7,-[3H]dihydroxy-1,2,3,4,-tetrahydronaphthalene ([3H] ADTN) binding to dopaminergic sites in rat, calf, and human brain. [3H]ADTN labeled two distinct types of dopaminergic binding sites in the brain striatum of the rat, calf, and human. Very low concentra...

Retinoids, metabolites and synthetic derivatives of vitamin A (retinol), have been shown to inhibit carcinogenesis in various epithelial tissues in animal model systems and to have clinical efficacy as chemotherapeutic agents against certain types ofcancer, including squamous cell carcinomas (SCCs). We examined the metabolism of[3H]retinol in normal human cell strains and SCC lines from the ora...

loc-Hydroxy[6-3H]vitamin D, has been synthesized with a specific activity of 4 Ci/mmol, and its metabolism in rats has been studied. It is rapidly converted to ln,25-dihydroxy[6-3H]vitamin D, in uiuo. Following an intravenous or oral dose, a maximal concentration of loc,25-dihydroxy[6-3H]vitamin D, is found 2 and 4 hours, respectively, before the maximal intestinal calcium transport response is...

A variety of evidence indicates that [3H]desipramine can label neuronal norepinephrine uptake sites in brain membranes. Pretreatment of rat cerebral cortical membranes with 0.3 M KCl increases the ratio of high affinity to low affinity saturable [3H]desipramine binding. With this improved tissue preparation, we have confirmed our earlier observation that the high affinity [3H]desipramine bindin...

Particulate fractions from fresh bovine corneal endothelium exhibited high affinity, specific binding by a potent muscarinic cholinergic radioligand, [3H]QNB. Particulate fraction binding sites exhibited half maximal binding at approximately 0.3 nM [3H]QNB and reached a maximal binding capacity of 820 fmoles/mg of protein at 3 nM [3H]QNB. Muscarinic cholinergic antagonists and agonists competed...

The correlation between the binding of NZ-105, a newly synthesized 1,4-dihydropyridine (DHP) derivative, on DHP receptors and its inhibitory activity on transmembrane 45Ca2+ uptake was investigated. 3H-NZ-105 bound rabbit aortic microsomes more slowly than did 3H-nitrendipine (3H-NTD): the association and dissociation rate constants of 3H-NZ-105 were about 70 times and 10 times less than those ...

AIMS To investigate glutamate receptor subtypes during alcohol withdrawal. METHODS Rats were exposed to severe alcohol intoxication for 84 h and then decapitated at 0, 12 and 36 h after the last alcohol dose (n = 7 per group). Alcohol was administered five times a day by intragastric intubation. The densities of N-methyl-D-aspartate (NMDA) and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionic a...

Transit of newly synthesized triacyl[3H]-glycerol through organelles of the secretory system leading to assembly into nascent very low density lipoproteins (VLDLs) or to cytoplasmic storage was investigated in chick hepatocytes. Cells in monolayer culture were pulse-labeled with [2-3H]glycerol, and after different periods of chase with unlabeled glycerol, the movement of triacyl[3H]glycerol thr...