Adenosine actions and adenosine receptors after 1 week treatment with caffeine.

After one week treatment with caffeine (20 mg/kg i.p.) the number of adenosine receptors, as determined by specific binding of (3H)-L-PIA, in rat cerebral cortical membranes was increased by about 25%.

2-chloroadenosine increases calcium mobilization from mouse calvaria in vitro.

The effect of 2-chloroadenosine on bone resorption and on cyclic AMP formation in murine calvarial bones in vitro was investigated. 2-Chloroadenosine increased the release of 45Ca from the cultured bones, but had no effect on dead bones, indicating that the effect is cell mediated. The adenosine analogue remained in the medium for 48 h and caused a transient stimulation of the formation of cyclic AMP.

Origin of adenosine released from rat vas deferens by nerve stimulation.

After labelling of vasa deferentia from intact rats with [3H] adenine there was a spontaneous outflow of labelled purines, mainly as adenosine inosine and hypoxanthine. There as a spontaneous outflow of endogenous adenosine and inosine amounting to 6 and 2 pmol/min from a single vas. The uptake inhibitor dipyridamole increased the rate of outflow to 27 and 28 pmol/min.

Purine levels in the intact rat brain. Studies with an implanted perfused hollow fibre.

A thin dialysis tube was implanted stereotaxically under halothane anesthesia in the caudate nucleus of Sprague-Dawley rats and perfused with Ringer solution at a rate of 2 microliters/min. Initially there was a high rate of purine outflow but after 1-2 h of perfusion the rate was essentially constant (anesthetized - adenosine 0.4 +/- 0.

Carbachol potentiates the cyclic AMP-stimulating effect of VIP in cat submandibular gland.

The effect of VIP and carbachol on cyclic AMP production were studied in isolated acini of the cat submandibular gland and guinea pig pancreas. VIP was almost 100 times more potent in stimulating cyclic AMP in the pancreas than in the submandibular salivary gland. Carbachol did not influence cyclic AMP in the pancreas while a 20-30% increase was seen in the submandibular gland.

On the mechanism by which theophylline inhibits histamine release from rat mast cells.

Theophylline (2.5 mM) did not influence the spontaneous release of histamine but inhibited histamine release induced by antigen, compound 48/80 or phosphatidylserine. The effect on 48/80-induced histamine release could not be reversed by increasing extracellular Ca2+.

Labetalol, a combined alpha- and beta-blocker, in hypertension of pregnancy.

Labetalol was given to women with hypertension of pregnancy in their last trimester to study its acute effect on circulation and metabolism. Seven women were given 50 mg labetalol i v. There was a significant decrease of blood pressure from a mean of 143/101 +/- 4/2 (SEM) to 127/88 +/- 5/2 mm Hg.

Metabolic and circulatory effects of intravenous and oral salbutamol in late pregnancy in diabetic and non-diabetic women.

The present study investigated the cardiovascular and metabolic "side-effects" of the beta 2-adrenoceptor stimulating drug salbutamol in the third trimester of pregnancy in diabetic and non-diabetic women. Salbutamol was administered either orally or as an intravenous infusion. Blood samples were collected for analyses of plasma cyclic AMP, insulin, C-peptide, and carbohydrate and lipid metabolites.

Metabolic and hormonal adjustments during hemorrhage in cats after interference with the sympatho-adrenal system.

The relative contribution of the splanchnic sympathetic innervation and the adrenal medulla for metabolism and hormone secretion during two different levels of hemorrhagic hypotension was investigated in 3 groups of anesthetized cats, viz, intact, adrenalectomized and splanchnicotomized (adrenalectomy + cutting of splanchnic nerves). In intact cats, hemorrhage caused very marked elevations of arterial plasma glucose, adrenaline, noradrenaline, dopamine, lactate, cAMP, glycerol and glucagon concentrations whereas plasma insulin fell to only 20% of control values. Adrenalectomy attenuated the glucose, adrenaline, noradrenaline and cAMP responses whereas the normal insulin inhibition was abolished.

Development of tolerance to oral salbutamol in the third trimester of pregnancy: a study of circulatory and metabolic effects.

1 The purpose of the study was to investigate whether a development of tolerance does occur or not to salbutamol-induced cardiovascular and metabolic effects after oral long term treatment in pregnancy. 2 Twenty-three women in late pregnancy were given an oral dose of 4 mg salbutamol in the morning after an overnight fast. Ten of the women had not been exposed to beta-adrenoceptor agonists earlier in their pregnancy (group A).

The antilipolytic effect of endogenous and exogenous adenosine in canine adipose tissue in situ.

The effects of adenosine, 2-Cl-adenosine, two adenosine uptake inhibitors (dipyridamole and dilazep) and the adenosine deaminase (ADA) inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) were studied on basal and stimulated lipolysis in subcutaneous adipose tissue. The basal lipolysis was unaffected by all agents. Lipolysis induced by nerve stimulation (4 Hz, 5 min) was dose-dependently antagonized (up to 100%) by close i.

Circulatory and metabolic effects of a combined alpha- and beta-adrenoceptor blocker (labetalol) in hypertension of pregnancy.

1 Seven women with hypertension of pregnancy were given the combined alpha- and beta-adrenoceptor blocking drug labetalol (50 mg i.v.) in their last trimester.

Early changes in ATP and cyclic AMP levels in experimental critical skin flaps.

A cranially based pedicle skin flap, 2 cm wide and 7 cm long, was prepared in the midline of the rat dorsum. The contents of ATP and cyclic AMP were determined in the proximal, middle and distal parts of the flap. The basal level of ATP was 1.

Quinacrine and release of purines from the rat hypothalamus.

The acridine derivative quinacrine accumulates in certain endocrine cells and nerve endings. It has been suggested that it binds to ATP stored in granules in such cells. For this reason the uptake and release of quinacrine and the ATP-precursor adenine was studied in slices and in crude synaptosomes from the rat hypothalamus.

Regulation of thymocyte proliferation: effects of L-alanine, adenosine and cyclic AMP in vitro.

Thymocyte proliferation in culture was studied by measuring the mitotic activity at hourly intervals during two periods, 0-13 and 18-30 h after the start of incubation. In particular, we investigated the effect of increased levels of cyclic AMP which are generated during preparation of the cells due to influence of endogeneously released adenosine. This cycle AMP surge, which could be blocked by combined treatment with adenosine deaminase and theophylline, caused a transient inhibition of proliferation at a stage 4 h prior to mitosis, suggesting a cyclic AMP-sensitive step in that part of the cell cycle.

Role of adenosine in adipose tissue circulation.

The vasodilatory effect of adenosine and some related compounds were studied in subcutaneous adipose tissue in situ. The effects of three drugs that inhibit adenosine elimination; two adenosine uptake blockers, dipyridamole and dilazep, the adenosine deaminase inhibitor, EHNA, were also studied. Plasma levels of adenosine were simultaneously determined by HPLC.

Alkylxanthines elevate hippocampal excitability. Evidence for a role of endogenous adenosine.

The effects of four xanthines (theophylline, 8-phenyltheophylline, isobutylmethylxanthine (IBMX), and 7-benzyl-IBMX) were studied in the hippocampal slice in vitro. These agents increased the excitability of this preparation with 8-phenyltheophylline being the most potent, 7-benzyl-IBMX the least potent, and theophylline and IBMX having intermediate potencies. A similar rank order was observed in terms of the potencies of these xanthines in antagonizing a) electrophysiological responses to adenosine, and b) adenosine-stimulated cyclic AMP formation.

Insulin-induced hypoglycaemia in diabetic women during late pregnancy and one year post partum.

Insulin (0.1 IW/kg) later followed by glucose was injected intravenously in nine diabetic women in the supine position both during pregnancy and one year post partum. C-peptide was present in five subjects, indicating some residual beta-cell function.

Evidence against a role of cyclic nucleotides in the regulation of anaphylactic histamine release in isolated rat mast cells.

The effect of different phosphodiesterase (PDE) inhibitors on the antigen or 48/80 induced histamine release from isolated Hooded Lister rat mast cells was tested. The unselective PDE inhibitors theophylline (2.5 mM) and IBMX (0.