Search Results
You are looking at 1 - 3 of 3 items for
- Author: ES Vizi x
- Refine by access: All content x
Search for other papers by B Sperlagh in
Google Scholar
PubMed
Search for other papers by Z Mergl in
Google Scholar
PubMed
Search for other papers by Z Juranyi in
Google Scholar
PubMed
Search for other papers by ES Vizi in
Google Scholar
PubMed
Search for other papers by GB Makara in
Google Scholar
PubMed
It is now widely accepted that ATP functions as a signalling substance in the nervous system. The presence of P2 receptors mediating the action of extracellular ATP in brain regions involved in hormonal regulation raises the possibility that a similar role for ATP might also exist in the neuroendocrine system. In this study, the release from the rat isolated neurohypophysis preparation of endogenous ATP, oxytocin and vasopressin (AVP) were measured simultaneously using luciferin-luciferase and RIA techniques. After 70 min preperfusion, electrical field stimulation caused a rapid increase in the amount of ATP in the effluent and the release of AVP and oxytocin also increased stimulation-dependently. Inhibition of voltage-dependent Na+ channels by tetrodotoxin (1 microM) reduced the stimulation-evoked release of AVP and oxytocin; however, the evoked release of ATP remained unaffected. The effect of endogenous ATP on the hormone secretion was tested by suramin (300 microM), the P2 receptor antagonist. Suramin significantly increased the release of AVP, and the release of oxytocin was also enhanced. ATP, when applied to the superfusing medium, decreased the release of AVP, but not that of oxytocin, and its effect was prevented by suramin. ATP (60 nmol), added to the tissues, was readily decomposed to ADP, AMP and adenosine measured by HPLC combined with ultraviolet light detection, and the kinetic parameters of the enzymes responsible for inactivation of ATP (ectoATPase and ecto5'-nucleotidase) were also determined (Km=264+/-2.7 and 334+/-165 microM and vmax=6.7+/-1.1 and 2.54+/-0.24 nmol/min per preparation (n=3) for ectoATPase and ecto5'-nucleotidase respectively). Taken together, our data demonstrate the stimulation-dependent release, P2 receptor-mediated action and extracellular metabolism of endogenous ATP in the posterior lobe of the hypophysis and indicate its role, as a paracrine regulator, in the local control of hormone secretion.
Search for other papers by A Janossy in
Google Scholar
PubMed
Search for other papers by E Orso in
Google Scholar
PubMed
Search for other papers by KS Szalay in
Google Scholar
PubMed
Search for other papers by Z Juranyi in
Google Scholar
PubMed
Search for other papers by M Beck in
Google Scholar
PubMed
Search for other papers by ES Vizi in
Google Scholar
PubMed
Search for other papers by GP Vinson in
Google Scholar
PubMed
Using histochemical and immunocytochemical methods, cholinergic nerve fibres were demonstrated in the rat adrenal cortex, primarily in the capsule and zona glomerulosa, and in the medulla. Some terminated among the glomerulosa cells or around blood vessels. Occasional fibres were also seen in the fasciculata, ending in islets of chromaffin tissue without ramifications on cortical cells. To clarify the role of cholinergic innervation, a microvolume perifusion system was used to study steroid production by the rat adrenal capsule-glomerulosa. Acetylcholine (ACh) itself had no reproducible effects; however, since variable amounts of endogenous ACh were present, the actions of antagonists were also studied. The M1 muscarinic receptor antagonist pirenzepine (10 and 100 microM) stimulated aldosterone secretion. This stimulation was abolished by co-incubation with carbachol, the M1 agonist McN A-343 and by atropine. We found that the action of pirenzepine was blocked by nifedipine (Ca2+ channel blocker), suggesting that pirenzepine (through release of endogenous ACh) provides an acute stimulus by enhancing Ca2+ inflow. Hemicholine, a choline uptake blocker, reduced the stimulatory effect of pirenzepine on steroid secretion, confirming that stimulation was of neural origin. Neither the non-selective muscarinic receptor antagonist atropine, the selective M1-M3 muscarinic receptor antagonist 4-DAMP, nor the selective M2 muscarinic receptor antagonist methoctramine influenced aldosterone output. Receptor-binding studies revealed the existence of M3 receptors in capsule-glomerulosa homogenates. We conclude that pirenzepine acts on presynaptic M1 autoreceptors to increase spontaneous ACh release from varicose axon terminals that lie in close proximity to the glomerulosa cells. In turn ACh may thus stimulate steroidogenesis acutely through M3 receptors. These results support the concept of a direct cholinergic influence on zona glomerulosa function in the rat.
Search for other papers by ES Vizi in
Google Scholar
PubMed
Search for other papers by J Szelenyi in
Google Scholar
PubMed
Search for other papers by ZS Selmeczy in
Google Scholar
PubMed
Search for other papers by Z Papp in
Google Scholar
PubMed
Search for other papers by ZH Nemeth in
Google Scholar
PubMed
Search for other papers by G Hasko in
Google Scholar
PubMed
It is increasingly apparent that there is a bidirectional interaction between the maternal immune system and the reproductive system during pregnancy. Pregnancy is associated with a suppression of maternal specific immune responses, which process underlies the protection of fetal tissues expressing paternally inherited alloantigens. However, recent evidence indicates that the suppression of specific, lymphocyte-mediated immune responses during pregnancy is accompanied by activation of the non-specific arm of the maternal immune response. In the present study, we have investigated the effect of pregnancy on the non-specific immune response induced by bacterial lipopolysaccharide (LPS, endotoxin) in mice. Pregnancy enhanced the LPS-induced production of proinflammatory cytokines, including tumor necrosis factor-alpha, interleukin (IL)-6, and interferon-gamma. On the other hand, LPS-induced levels of the anti-inflammatory cytokine IL-10 were suppressed in pregnant mice. These alterations in cytokine production correlated with an increased susceptibility for endotoxemic mortality in the pregnant mice. Although adrenergic receptors are important regulators of cytokine production in non-pregnant mice, the alpha(2)- and the beta-adrenoceptor-mediated modulation of cytokine production ceases to operate during pregnancy associated with severe endotoxemia. These data may explain how excessive activation of the non-specific immune responses during pregnancy can contribute to the increased severity of some maternal diseases, including septic shock, and can be an important pathophysiological factor in disseminated intravascular coagulation or preeclampsia.