1 The aim of the present study was to determine the eect of nitric oxide (NO) on angiotensinconverting enzyme (ACE) activity. 2 A biochemical study was performed in order to analyse the eect of the NO-donors, SIN-1 and diethylamine/NO (DEA/NO), and of an aqueous solution of nitric oxide on the ACE activity in plasma from 3-month old male Sprague-Dawley rats and on ACE puri®ed from rabbit lung. SIN-1 signi®cantly inhibited the activity of both enzymes in a concentration-dependent way between 1 and 100 mM. DEA/ NO inhibited the activity of puri®ed ACE from 0.1 mM to 10 mM and plasma ACE, with a lower potency, between 1 and 100 mM. An aqueous solution of NO (100 and 150 mM) also inhibited signi®cantly the activity of both enzymes. Lineweaver-Burk plots indicated an apparent competitive inhibition of HipHis-Leu hydrolysis by NO-donors. 3 Modulation of ACE activity by NO was also assessed in the rat carotid artery by comparing contractions elicited by angiotensin I (AI) and AII. Concentration-response curves to both peptides were performed in arteries with endothelium in the presence of the guanylyl cyclase inhibitor, ODQ (10 mM), and the inhibitor of NO formation, L-NAME (0.1 mM). NO, which is still released from endothelium in the presence of 10 mM ODQ, elicited a signi®cant inhibition of AI contractions at low concentrations (1 and 5 nM). In the absence of endothelium, 1 mM SIN-1 plus 10 mM ODQ, as well as 10 mM DEA/NO plus 10 mM ODQ induced a signi®cant inhibition on AI-induced contractions at 1 and 5 nM and at 1 ± 100 nM, respectively. 4 In conclusion, we demonstrated that (i) NO and NO-releasing compounds inhibit ACE activity in a concentration-dependent and competitive way and that (ii) NO release from endothelium physiologically reduces conversion of AI to AII.
Adenosine transport was measured in human cultured umbilical artery smooth muscle cells, isolated from non‐diabetic or gestational diabetic pregnancies, under basal conditions and after pretreatment in vitro with insulin.
Adenosine transport in non‐diabetic smooth muscle cells was significantly increased by insulin (half‐maximal stimulation at 0.33 ± 0.02 nm, 8 h) and characterized by a higher maximal rate (Vmax) for nitrobenzylthioinosine (NBMPR)‐sensitive (es) saturable nucleoside transport (17 ± 5 vs. 52 ± 12 pmol (μg protein)−1 min−1, control vs. insulin, respectively) and maximal binding sites (Bmax) for [3H]NBMPR (0.66 ± 0.07 vs. 1.1 ± 0.1 fmol (μg protein)−1, control vs. insulin, respectively), with no significant changes in Michaelis‐Menten (Km) and dissociation (Kd) constants.
In contrast, in smooth muscle cells from diabetic pregnancies, where the values of Vmax for adenosine transport (59 ± 4 pmol (μg protein)−1 min−1) and Bmax for [3H]NBMPR binding (1.62 ± 0.16 fmol (μg protein)−1) were significantly elevated by comparison with non‐diabetic cells, insulin treatment (1 nm, 8 h) reduced the Vmax for adenosine transport and Bmax for [3H]NBMPR binding to levels detected in non‐diabetic cells.
In non‐diabetic cells, the stimulatory effect of insulin on adenosine transport was mimicked by dibutyryl cGMP (100 nm) and reduced by inhibitors of phosphatidylinositol 3‐kinase (10 nm wortmannin), nitric oxide synthase (100 μmNG‐nitro‐l‐arginine methyl ester, l‐NAME) or protein synthesis (1 μm cycloheximide), whereas inhibition of adenylyl cyclase (100 μm SQ‐22536) had no effect.
Wortmannin or SQ‐22536, but not l‐NAME or cycloheximide, attenuated the inhibitory action of insulin on the diabetes‐induced stimulation of adenosine transport.
Protein levels of inducible NO synthase (iNOS) were similar in non‐diabetic and diabetic cells, but were increased by insulin (1 nm, 8 h) only in non‐diabetic smooth muscle cells.
Our results suggest that adenosine transport via the es nucleoside transporter is modulated differentially by insulin in either cell type. Insulin increased adenosine transport in non‐diabetic cells via NO and cGMP, but inhibited the diabetes‐elevated adenosine transport via activation of adenylyl cyclase, suggesting that the biological actions of adenosine may be altered under conditions of sustained hyperglycaemia in uncontrolled diabetes.
A link between stressful life events and development or exacerbation of depression has been established via a large body of evidence. An alteration in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis in depression has also been associated with an increase in cortisol secretion. As arginine-vasopressin (AVP) plays an important role in the activation of HPA axis during stress, the present study investigated ACTH and cortisol secretory response induced by an AVP-related peptide desmopressin (ddAVP) in patients with major depression. Prior to antidepressant treatment, endocrinological parameters were evaluated and correlated with the clinical response to venlafaxine treatment, which offers a dual antidepressant action. Depressive patients with no other psychiatric pathology were evaluated with 17-item Hamilton Depression Scale (HAM-D) in order to follow-up the response to venlafaxine. After 1 wk of treatment, 60% of patients reduced their initial HAM-D score to at least 25%; this group was classified as early responders. The other group (40%) started to reduce significantly their HAM-D score after 3 wk of treatment and was classified as late responders. After 6 wk of treatment both groups have reduced HAM-D score to at least 25% of the baseline score. Prior to the pharmacological treatment, both early and late responders showed salivary cortisol rhythm and urinary free cortisol (UFC) in 24-h similar to healthy subjects. However, we did observe differences in basal ACTH secretion, showing that the late responder group had higher basal ACTH than both early responders and controls. The ddAVP challenge promoted a robust secretion of ACTH only in late responders, suggesting a different sensitivity of pituitary vasopressin receptor. The differences in clinical response to venlafaxine among depressive patients seem to be related to endocrinological parameters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.