Effect of estradiol on Ca2+ exit from intracellular stores in swine granulose cells activated by theophylline and prolactin is investigated with using fluorescent Ca2+ sensitive probe chlortetracycline. It was shown that prolactin and theophylline stimulated Ca2+ exit from intracellular stores. In absence of estradiol if we treatment of oocytes by theophylline and prolactin together we have not found influence at Ca2+ exit from intracellular stores. In the presence of estradiol we had opposite results: we tested additional Ca2+ exit at common action of theophylline and prolactin. Protein kinase C influences on Ca2+ exit from intracellular stores during common affect of theophylline and prolactin only in the presence of estradiol. Protein kinase A does not influence this process. The obtained data indicate an influence of estradiol on Ca2+ exit from intracellular stores in swine granulose cells stimulated by joint action of prolactin and theophylline.

BACKGROUND. Preconditioning (5 minutes of ischemia followed by 10 minutes of recovery) renders the heart very resistant to infarction from subsequent ischemia. This study tests whether adenosine receptors might mediate preconditioning protection. METHODS AND RESULTS. We examined the effect on infarct size of pretreatment with either of two adenosine receptor antagonists in both control and preconditioned in situ rabbit hearts. Hearts underwent 30 minutes of regional ischemia plus 3 hours of reperfusion, and infarct size was measured with tetrazolium. Infarct size averaged 39% of the zone at risk in controls but only 8% in preconditioned hearts. Preconditioned and nonpreconditioned hearts receiving either blocker had infarcts not different in size from the controls. A 5-minute intracoronary infusion of adenosine was as effective as 5 minutes of ischemia in protecting parabiotically perfused isolated hearts against infarction from a 45-minute ischemic insult. Similarly, intracoronary infusion of N6-1-(phenyl-2R-isopropyl)adenosine, an A1-selective adenosine receptor agonist, at a dose that delayed conduction but did not dilate the coronary vessels, also limited infarct size. The protection disappeared when we reduced the coronary concentration of drug by intravenous infusion of adenosine, indicating that cardiac rather than peripheral receptors were involved in the protection. CONCLUSIONS. We conclude that adenosine released during the preconditioning occlusion stimulates cardiac A1 receptors, which leaves the heart protected against infarction even after the adenosine has been withdrawn.

The adenylate cyclase activity of intact pigeon erythrocytes begins to rise after about 20 min of exposure to cholera toxin. The maximum rate at which the cyclase activity increases appears to be limited by the number of toxin molecules which can reach an intracellular target. If the erythrocytes are made permeable to the toxin by a bacterial hemolysin, no such limit exists, and adenylate cyclase activity starts to rise immediately upon the addition of toxin, and continues to rise to a maximum at an initially constant rate which is dependent upon the concentration of toxin. On lysed erythrocytes, the addition of cholera antitoxin immediately prevents any further rise in adenylate cyclase activity, but does not reverse any activation already achieved. Erythrocyte lysates may also be activated by isolated peptide A1 of cholera toxin, although activation of adenylate cyclase of intact erythrocytes requires the complete toxin molecule. In the intact cells, toxin first attaches by its Component B to surface receptors of which there are about 30 per erythrocyte. Subsequently, peptide A1 but not Component B is inserted into the erythrocyte. It takes only about 1 min at 37 degrees for peptide A1 to be sufficiently deep within the cell membrane to be inaccessible to extracellular antitoxin, but its complete transit through the membrane appears to take longer. The surface receptors are used only once, for they remain blocked by Component B. The number of receptors available on the surface may be increased by soaking cells in ganglioside GM1. Cholera toxin also decreases the rate of apparently spontaneous loss of adenylate cyclase activity and increases the response to epinephrine. Theophylline inhibits the action of cholera toxin.

The effects of local injections of drugs into terminal areas of the mesolimbic dopamine system were investigated. Bilateral administration of dopamine, but not of noradrenaline and serotonin, into the nucleus accumbens of non-pretreated rats resulted in stimulation of locomotor activity. No clear or only minor effects were seen after injections of the dopamine metabolites 3-methoxytyramine, DOPAC and HVA and after injections of media with different pH and osmolality. d-Amphetamine proved more effective than dopamine in producing locomotor stimulation, whereas both stimulant and depressant effects were observed following injection of apomorphine into the nucleus accumbens. ET 495 and the noradrenaline agonists clonidine, phenylephrine and isoprenaline did not enhance locomotor activity, but theophylline was effective. Pretreatment with haloperidol, but not with clozapine, significantly reduced the effects of dopamine and theophylline. Locomotor stimulation was also found following bilateral administration of dopamine, d-amphetamine and apomorphine into the tuberculum olfactorium, whereas noradrenaline, serotonin and ET 495 produced no, or rather depressant effects. These results provide further evidence for an important role of the mesolimbic dopamine system with respect to locomotor activity.

1. The action of catecholamines on the transport and the distribution of Na and K and the resting membrane potential (E(M)) has been investigated in soleus muscles isolated from fed rats.2. In a substrate-free Krebs-Ringer bicarbonate buffer adrenaline (ADR)(6 x 10(-6)M) increased (22)Na efflux by 83%,(42)K influx by 34%, and E(M) by 10%. Similar effects were exerted by noradrenaline (NA), phenylephrine, salbutamol and isoprenaline. The effects of ADR on Na-K transport and E(M) were suppressed by ouabain (10(-3)M) and propranolol (10(-5)M), but not by thymoxamine (10(-5)M) or tetracaine (10(-4)M).3. Following 90 min of incubation in the presence of ADR (6 x 10(-6)M), the intracellular K/Na-ratio was increased threefold. NA produced almost the same change, and both catecholamines seem to induce a new steady-state distribution of Na and K which can be maintained for several hours in vitro.4. The effect of ADR on (22)Na efflux and E(M) could be detected at concentrations down to 6 x 10(-9) and 6 x 10(-10)M, respectively, and half-maximum increase was obtained at around 2 x 10(-8)M. NA was at least one order of magnitude less potent.5. The effect of low concentrations of ADR on (22)Na efflux was potentiated by theophylline (2 mM). When added together, dibutyryl-cyclic AMP and theophylline mimicked the action of ADR on (22)Na efflux,(42)K influx, Na/K content and E(M). Ouabain (10(-3)M) also suppressed the effect of dibutyryl-cyclic AMP and theophylline on Na-K transport.6. Following the addition of ouabain (10(-3)M), E(M) rapidly dropped from a mean of -71 to -63 mV, and then showed a slow linear fall for up to 4hr.7. The hyperpolarization induced by ADR was associated with a decrease in membrane conductance,(22)Na influx and (42)K efflux. The time course and the response to ouabain suggests that all of these effects are secondary to stimulation of the active coupled transport of Na and K.8. It is concluded that in rat soleus muscle, the active Na-K transport is electrogenic and susceptible to stimulation by catecholamines via beta-adrenoceptors. This effect is mediated by adenyl cyclase activation and may account for the increase in E(M) and the intracellular K/Na ratio.