Adenosine may be a physiological modulator of vascular smooth muscle tone, sympathetic neurotransmission, renin release, and renal and cardiac function. To facilitate the elucidation of the physiological role of adenosine, a microassay for adenosine was developed that allows accurate quantitation of adenosine in 75 microliters of rat plasma, thus permitting multiple determinations of plasma ade...

The adenosinergic system is involved in many important physiological functions. Adenosine exerts its extracellular effects through four types of G-protein-coupled receptors: A(1), A(2A), A(2B) and A(3). Adenosine acts as an important regulator of metabolic processes. In the brain adenosine mediates prominent neuroprotective functions via the adenosine A(1) receptor. Whereas the pharmacological ...

The effect of adenosine on the function of the heart in Octopus vulgaris was studied using an isolated heait preparation. Bolus injections of adenosine or AMP (adenosine precursor) induced both positive chronotropic and inotropic effects. The maximum inotropic effect preceded the maximum chronotropic effect. The impermeable adenosine analogue 2-chloroadenosine elicited a similar effect, while t...

Previous studies have shown that in vitro adenosine enhances histamine release from activated human lung mast cells obtained by enzymic dispersion of lung parenchyma. However, adenosine alone has no effect on histamine release from these cells. Given the evidence for direct activation of mast cells after endobronchial challenge with adenosine and previous studies indicating that mast cells obta...

The aim of this investigation was to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels. Rat preglomerular vascular smooth muscle cells were incubated with adenosine, guanosine, or both. Guanosine (30 μmol/l) per se had little effect on extracellular adenosine levels. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) were 0.125 ± 0....

A recent study (American Journal of Physiology-Cell Physiology 304: C406-C421, 2013) suggests that extracellular guanosine increases extracellular adenosine by modifying the disposition of extracellular adenosine ("guanosine-adenosine mechanism") and that the guanosine-adenosine mechanism is not mediated by classical adenosine transport systems (SLC28 and SLC29 families) nor by classical adenos...

The renal extracellular 2',3'-cAMP-adenosine and 3',5'-cAMP-adenosine pathways (extracellular cAMPs→AMPs→adenosine) may contribute to renal adenosine production. Because mouse kidneys provide opportunities to investigate renal adenosine production in genetically modified kidneys, it is important to determine whether mouse kidneys express these cAMP-adenosine pathways. We administered (renal art...

Adenosine vasoconstricts preglomerular arterioles via adenosine A1 receptors. Because adenosine also activates adenosine A2 receptors, its overall renal vascular actions are complex and not fully understood. The present study was performed to determine the relative contributions of adenosine A1 and A2a receptors to the responsiveness of the renal microvasculature to adenosine. Afferent and effe...

Adenosine produced a severalfold amplification of luteinizing hormone (LH)-stimulated cAMP accumulation and progesterone secretion in rat luteal cells, but showed no similar effect on LH-stimulated cAMP accumulation and androgen secretion in Leydig cells. In the absence of LH, adenosine produced a small but significant stimulation of cAMP accumulation and steroid secretion in both luteal and Le...

There is a growing body of evidence suggesting that the neuromodulator adenosine is involved in drug addiction and withdrawal and that adenosine signaling pathways may offer new targets for therapeutic treatments of addiction. Recent studies have suggested that chronic exposure to drugs of abuse may alter adenosine metabolism in the nucleus accumbens, a brain region critically involved in drug ...