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M C Michel

Publications and source records attributed to M C Michel.

At least 109 records · Page 6Linked to original sources
PubMed1998

Bradykinin may be involved in neuropeptide Y-induced diuresis, natriuresis, and calciuresis.

Neuropeptide Y (NPY) can cause diuresis, natriuresis, and calciuresis in rats independently of the pressure-natriuresis mechanism (A. Bischoff and M. C. Michel. Pflügers Arch. 435: 443-453, 1998). Because this is seen in systemic but not intrarenal NPY infusion, we have investigated the possible mediator of tubular NPY effects in anesthetized rats. In the present study, infusion of NPY (2 micrograms . kg-1 . min-1) enhanced renovascular resistance by approximately 8 mmHg . ml-1 . min and enhanced urine and sodium excretion by approximately 450 microliter/15 min and approximately 60-85 micromol/15 min, respectively. Acute renal denervation did not alter renovascular or tubular NPY effects, indicating that a neuronally released mediator is not involved. Treatment with the angiotensin II-receptor antagonist losartan prevented the decline of the renovascular response with time but did not modify tubular NPY effects. The bradykinin B2-receptor antagonist icatibant accelerated the decline of the renovascular NPY effects with time; concomitantly, it attenuated NPY-induced diuresis and natriuresis and abolished NPY-induced calciuresis. The converting-enzyme inhibitor ramiprilat prevented the decline of the renovascular response with time; concomitantly, it magnified the NPY-induced diuresis, natriuresis, and calciuresis. We conclude that bradykinin may be involved in NPY-induced diuresis, natriuresis, and, in particular, calciuresis.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

A double-blind comparison of terazosin and tamsulosin on their differential effects on ambulatory blood pressure and nocturnal orthostatic stress testing.

OBJECTIVES: This single-centre, double-blind, randomized parallel-group study compared ambulatory blood pressure (AMBP) and heart rate (HR) profiles and responses to orthostatic testing (OT) for recommended regimens of tamsulosin (TAM, modified release formulation) and terazosin (TER), two alpha1-adrenoceptor antagonists that differ in their selectivity for alpha1-adrenoceptor subtypes, pharmacokinetic properties and recommended posology for the treatment of lower urinary tract symptoms (LUTS) suggestive of benign prostatic obstruction (BPO). METHODS: 50 elderly normotensive male volunteers (mean age 68 years, range 61-78; 27 had LUTS) entered a single-blind 24-hour placebo run-in followed by a 15-day double-blind treatment in which the TER group received a 1-week treatment with 1 mg, then 1 week with 2 mg and finally a last dose of 5 mg, each dose administered once daily in the evening, while TAM subjects received 0.4 mg once daily after breakfast throughout. Subjects had AMBPs and OT while hospitalized on four occasions: during the placebo run-in and subsequent to the first dose of 1, 2 and 5 mg TER or at corresponding times under TAM. Regular OT (blood pressure after 5 min supine and after 2 min standing) was carried out between 6:00 and 6:30 a.m.; 'nocturial' OT took place whenever the subject had to leave the bed at night to void. RESULTS: The baseline blood pressure values were slightly higher in the TAM group, but under treatment there was little difference between the treatments with regard to circadian changes in AMBP and HR. Under TER, there were 10 incidents of symptomatic hypotensive OT in 9 subjects (2 with syncope); furthermore, there were 24 events of asymptomatic exaggerated (> or = 20 mm Hg) decrease in systolic blood pressure in 12 subjects. With TAM in contrast, there was only 1 subject who experienced symptomatic hypotensive OT on 3 occasions (this subject had a previous history of vertigo and ought not to have been included); 7 subjects on TAM showed 16 incidents of asymptomatic hypotensive OT. The difference between TER and TAM was statistically significant for the number of subjects with positive symptomatic OT (p = 0.011). CONCLUSION: Once-daily dosing of TAM after breakfast at a fixed dose level (0.4 mg) offers a more efficient protection against undesired cardiovascular extension effects in the normotensive elderly treated for LUTS suggestive of BPO than the usually recommended treatment schedule of TER with step-up doses (1-5 mg) administered at night.

Adrenergic alpha-Antagonists↗
PubMed1998

Tamsulosin: real life clinical experience in 19,365 patients.

OBJECTIVE: To compare the efficacy, global tolerability and blood pressure effects of tamsulosin (0.4 mg once daily) in subgroups of patients with lower urinary tract symptoms (LUTS) suggestive of benign prostatic obstruction (BPO). METHODS: Data from two open-label, observational studies (Study I: 9,507 patients treated for 4 weeks, Study II: 9,858 patients treated for 12 weeks) were analyzed to compare efficacy, global tolerability and effects on blood pressure in subgroups of patients. RESULTS: The efficacy of tamsulosin was largely unaffected by age or previous phytotherapy; in patients with severe symptoms, the efficacy was at least as large as in those with mild or moderate symptoms. More than 90% of patients reported a good or very good tolerability; in a multivariate analysis, this was slightly reduced in patients with concomitant disease but not affected by antihypertensive co-medication or baseline blood pressure. In patients without co-morbidity or co-medication, the tamsulosin-induced blood pressure reductions were similar to those previously reported for placebo treatment; mean additional blood pressure reductions in patients with concomitant disease or medication was not more than 2 mm Hg. Patients who had previously been treated with beta-sitosterol, other plant extracts or finasteride reported tamsulosin to be more effective than their previous treatment. Patients who had previously received beta-sitosterol or other plant extracts rated the global tolerability of tamsulosin to be similar to that of their previous treatment, while those who had previously received finasteride or other alpha 1-adrenoceptor antagonists rated the global tolerability of tamsulosin to be significantly better than that of their previous treatment. CONCLUSIONS: We conclude that tamsulosin is efficacious in all types of patients with LUTS suggestive of BPO. It is globally well tolerated and has marginal effects on blood pressure, including the vast majority of patients with cardiovascular comorbidity, diabetes or on antihypertensive comedication.

Adrenergic alpha-Antagonists↗
PubMed1998

Neuropeptide Y lowers blood glucose in anaesthetized rats via a Y5 receptor subtype.

We have investigated the receptor subtype mediating effects of neuropeptide Y (NPY) on blood glucose concentrations. In anaesthetized rats a 120 min i.v. infusion of 2 microg/kg/min NPY lowered blood glucose by 26 mg/dl. This was mimicked by the same dose of peptide YY (PYY), NPY2-36, PYY3-36 and [Leu31,Pro34]NPY but not by NPY13-36, PYY13-36 or rat or human pancreatic polypeptide. The effects of NPY and [Leu31,Pro34]NPY were not inhibited by 10 microg/kg/min BIBP 3226. Neither treatment significantly altered plasma insulin concentrations. We conclude that NPY lowers blood glucose concentrations via a Y5 receptor subtype, i.e. a subtype which has also been implicated in stimulation of food intake.

Animals↗
PubMed1998

Stimulation of mitogen activated protein kinase and cellular proliferation in renal proximal tubular cells.

We have studied activation of mitogen-activated protein kinase (MAP kinase) and [3H]-thymidine uptake as a marker for cellular proliferation in a proximal tubular cell line of the American Opossum kidney (OK cells). Adrenaline, serotonin, epidermal growth factor and insulin all stimulated MAP kinase and [3H]-thymidine uptake. This stimulation of cellular proliferation was markedly reduced by an inhibitor of the MAP kinase pathway, PD 98059. Epidermal growth factor stimulated MAP kinase activity more effectively than the other agonists, but all four had similar effects on OK cellular proliferation. These data indicate that amine neurotransmitters may be of similar importance for tubular regeneration as classical growth factors.

Animals↗
PubMed1998

Protein kinase C does not mediate phenylephrine-induced down-regulation of Madin-Darby canine kidney cell alpha-1B adrenoceptors.

We examined the down-regulation of alpha-1B adrenoceptors in Madin-Darby canine kidney D1 (MDCK) cells with an emphasis on a possible role of protein kinase C. The alpha-1 adrenoceptor agonist phenylephrine (1-100 microM) concentration-dependently down-regulated alpha-1B adrenoceptors in MDCK cells. Down-regulation by 100 microM phenylephrine was detectable after 2 hr and maximal after 8 to 24 hr. The receptor down-regulation was accompanied by a decrease in phenylephrine-stimulated inositol phosphate formation but not by an altered expression of immunodetectable Gq/11 alpha subunits. Even though alpha-1B adrenoceptor and P2 purinergic receptor stimulation promote prostaglandin E2 formation, receptor down-regulation was not prevented by indomethacin (10 microM) treatment but was partly mimicked by treatment with the purinergic receptor agonists adenosine-5'-O-(3-thio)triphosphate and 2-methylthio-ATP (300 microM each). Phorbol-12-myristate-13-acetate (1-100 nM) concentration-dependently down-regulated MDCK alpha-1B adrenoceptors to a greater extent than did phenylephrine. Three protein kinase C inhibitors, H7 (100 microM), staurosporine (100 nM) and KT5926 (1 microM), markedly attenuated receptor down-regulation promoted by phorbol ester but did not affect that by phenylephrine. Two inhibitors of Ca++/calmodulin protein kinase pathways, KT5926 (1 microM) and W-7 (30 microM), also failed to prevent phenylephrine-induced down-regulation of alpha-1B adrenoceptors. We conclude that agonist-induced down-regulation of MDCK cell alpha-1B adrenoceptors is mimicked by a protein kinase C-activating phorbol ester but that the second messenger kinases protein kinase C and Ca++/calmodulin protein kinase do not mediate agonist-induced down-regulation of the alpha-1B adrenoceptor.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Indomethacin inhibits the natriuretic effects of neuropeptide Y in anesthetized rats.

Neuropeptide Y (NPY) is a unique modulator of renal function that enhances urine flow and sodium excretion despite marked reductions in renal blood flow. We investigated whether the cyclooxygenase inhibitor indomethacin alters the renal NPY effects in anesthetized rats. Treatment with 5 mg/kg indomethacin i.p. lowered urinary prostaglandin excretion by approximately 85%. Systemic infusion of NPY elevated mean arterial pressure by approximately 15 mm Hg and renovascular resistance by approximately 8.0 mm Hg/ml/min, whereas the related peptide YY3-36 (PYY3-36) did not. Nevertheless, both peptides enhanced urine flow rate by approximately 250 and approximately 100 microl/15 min, respectively, and sodium excretion by approximately 15 micromol/15 min. Treatment with indomethacin did not affect NPY- and PYY3-36-induced alterations of systemic and renovascular hemodynamics but completely abolished NPY- and PYY3-36-induced diuresis and natriuresis. Endogenous creatinine clearance was not affected by any treatment. We conclude that cyclooxygenase-derived arachidonic acid metabolites are not involved in the systemic or renal hemodynamic effects of NPY and PYY3-36 but mediate NPY- and PYY3-36-induced diuresis and natriuresis.

Anesthesia↗
PubMed1998

Murine alpha1-adrenoceptor subtypes. I. Radioligand binding studies.

Alpha1-adrenoceptors were identified in murine tissues by [3H]prazosin saturation binding studies, with a rank order of cerebral cortex > cerebellum > liver > lung > kidney > heart > spleen, with the spleen not exhibiting detectable expression. Competition binding studies were performed with 5-methylurapidil, BMY 7378, methoxamine, (+)-niguldipine, noradrenaline, SB 216469 and tamsulosin. On the basis of monophasic low-affinity competition by BMY 7378, alpha1D-adrenoceptors were not detected at the protein level in any tissue. On the basis of competition studies with the alpha1A/alpha1B-discriminating drugs, alpha1B-adrenoceptors appeared to be the predominant or even the sole subtype in murine liver, lung and cerebellum, whereas murine cerebral cortex and kidney contained approximately 30% and 50% of alpha1A-adrenoceptors, respectively. The affinities of the various competitors in the murine tissues were quite similar to those reported from other species. The ratio of high- and low-affinity sites for tamsulosin did not in all cases match the percentages of alpha1A- and alpha1B-adrenoceptors detected by the other competitors; however, the low-affinity component of the tamsulosin competition curves was abolished in the cerebral cortex of alpha1B-adrenoceptor knockout mice. Treatment with chloroethylclonidine (10 microM, 30 min, 37 degrees C) inactivated the alpha1-adrenoceptors in all tissues by >75%. When the concentration-dependent inactivation of tissue alpha1B-adrenoceptors (liver) and tissue alpha1A-adrenoceptors (cerebral cortex from alpha1B-adrenoceptor knockout mice) was compared, alpha1A-adrenoceptors were only slightly less sensitive toward chloroethylclonidine than alpha1B-adrenoceptors. We conclude that murine tissues express alpha1A- and alpha1B-adrenoceptors, which are largely similar to those in other species. However, the tissue-specific distribution of subtypes may differ from that of other species.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1997

Decreased blood pressure response in mice deficient of the alpha1b-adrenergic receptor.

To investigate the functional role of different alpha1-adrenergic receptor (alpha1-AR) subtypes in vivo, we have applied a gene targeting approach to create a mouse model lacking the alpha1b-AR (alpha1b-/-). Reverse transcription-PCR and ligand binding studies were combined to elucidate the expression of the alpha1-AR subtypes in various tissues of alpha1b +/+ and -/- mice. Total alpha1-AR sites were decreased by 98% in liver, 74% in heart, and 42% in cerebral cortex of the alpha1b -/- as compared with +/+ mice. Because of the large decrease of alpha1-AR in the heart and the loss of the alpha1b-AR mRNA in the aorta of the alpha1b-/- mice, the in vivo blood pressure and in vitro aorta contractile responses to alpha1-agonists were investigated in alpha1b +/+ and -/- mice. Our findings provide strong evidence that the alpha1b-AR is a mediator of the blood pressure and the aorta contractile responses induced by alpha1 agonists. This was demonstrated by the finding that the mean arterial blood pressure response to phenylephrine was decreased by 45% in alpha1b -/- as compared with +/+ mice. In addition, phenylephrine-induced contractions of aortic rings also were decreased by 25% in alpha1b-/- mice. The alpha1b-AR knockout mouse model provides a potentially useful tool to elucidate the functional specificity of different alpha1-AR subtypes, to better understand the effects of adrenergic drugs, and to investigate the multiple mechanisms involved in the control of blood pressure.

Animals↗
PubMed1997

Comparison of adrenoceptor subtype expression in porcine and human bladder and prostate.

We have quantified and characterized alpha 1-, alpha 2- and beta-adrenoceptor subtypes in porcine bladder detrusor and bladder neck, human bladder detrusor, and porcine and human prostate. alpha 1-, alpha 2- and beta-adrenoceptor were identified in radioligand binding studies using [3H]prazosin, [3H]RX 821002 and [125I]iodocyanopindolol, respectively, as the radioligands. In porcine male and female detrusor and bladder neck and male prostate, adrenoceptors were detected in the order of abundance beta > alpha 2 >> alpha 1 (not detectable), with no major difference between the sexes or between detrusor and bladder neck. In human detrusor and prostate the order of abundance was beta > alpha 2 >> alpha 1 (not detectable) and beta >> alpha 1 > alpha 2, respectively. The alpha 2-adrenoceptors in all tissues were homogeneously of the alpha 2A-subtype as evidenced by competition binding studies with yohimbine, prazosin, ARC 239 and oxymetazoline. The beta-adrenoceptors represented a mixed population with a dominance of the beta 2-subtype in all tissues as demonstrated by competition binding with ICI 118,551 and CGP 20,712A. We conclude that pigs may be a suitable model for studies of detrusor function with respect to adrenoceptor expression. They may be less suitable for studies of bladder neck or prostate function.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1997

Influence of adrenoceptor and muscarinic receptor blockade on the cardiovascular effects of exogenous noradrenaline and of endogenous noradrenaline released by infused tyramine.

This study aimed firstly to compare the in vivo cardiovascular effects of exogenously administered and of endogenously released noradrenaline; secondly to characterize the adrenoceptors mediating these responses; thirdly to assess the influence of parasympathetic tone on the cardiovascular effects of noradrenaline. In two randomised placebo-controlled studies, healthy, young, male volunteers received intravenous (i.v.) infusions of noradrenaline at six incremental doses of 10-160 ng/kg/min and-in order to release endogenous noradrenaline-tyramine at four incremental doses of 5-20 micrograms/kg/min. Noradrenaline and tyramine were administered in the absence and presence of alpha 1-adrenoceptor blockade with doxazosin (2 mg p.o.), alpha 2-adrenoceptor blockade with yohimbine (15 mg p.o.), selective beta 1-adrenoceptor blockade with bisoprolol (15 mg p.o.) and muscarinic receptor blockade with atropine (1.5 micrograms/kg i.v. loading dose followed by 0.15 microgram/kg/min by i.v. infusion). Vasoconstrictor effects were assessed by measurement of diastolic blood pressure (Pdiast) and myocardial effects by measurement of systolic time intervals, namely the duration of electromechanical systole corrected for heart rate (QS2c). I.v. noradrenaline increased Pdiast (delta max 17 mmHg) and this was nearly completely suppressed by doxazosin but only slightly blunted by yohimbine. Noradrenaline also slightly shortened QS2c (delta max -22 ms), and this was potentiated by both doxazosin and yohimbine and completely blocked by biosprolol. I.v. tyramine reduced Pdiast (delta max -7 mmHg), which was not affected by alpha 1-adrenoceptor blockade, and profoundly shortened QS2c (delta max -104 ms) which was significantly correlated with a marked increase in systolic blood pressure (Psyst) (delta max 57 mmHg). The shortening of QS2c and the rise in Psyst were not influenced by alpha-adrenoceptor blockade but were antagonized by bisoprolol. Atropine potentiated the blood pressure rise and the shortening of QS2c induced by i.v. noradrenaline and converted the fall in Pdiast induced by i.v. tyramine into an increase. Thus the cardiovascular effects of exogenous noradrenaline are mainly characterized by alpha 1-adrenoceptor-mediated vasoconstriction and the actions of endogenous noradrenaline (released by i.v. tyramine) by beta 1-adrenoceptor-mediated positive inotropic effects. The rise in Psyst with i.v. tyramine most likely reflects positive inotropism and not a vascular "pressor' response.

Adrenergic Antagonists↗
PubMed1997

Is alpha1D-adrenoceptor protein detectable in rat tissues?

We have used the alpha1D-adrenoceptor selective antagonist, BMY 7378, the alpha1D-selective agonists, adrenaline and phenylephrine, the alpha1A-selective antagonists, (+)-niguldipine, SB 216469 and WB4101, and the non-subtype-selective alpha1-adrenoceptor antagonist, nemonapride, to investigate the presence of alpha1D-adrenoceptors in rat tissues at the protein level. Radioligand binding studies using [3H]prazosin as the radioligand were performed in three tissues containing alpha1D-adrenoceptor mRNA, spleen, cerebral cortex and kidney, and in comparison in one tissue not containing alpha1D-adrenoceptor mRNA, liver. Cerebral cortex and kidney were also studied upon alpha1B-adrenoceptor inactivation by chloroethylclonidine treatment (10 microM, 30 min, 37 degrees C). Experiments with cloned rat alpha1-adrenoceptor subtypes transiently expressed in COS cells confirmed the known selectivity of the investigated drugs for alpha1-adrenoceptor subtypes or the lack thereof of nemonapride. Accordingly nemonapride had steep and monophasic competition curves in all native and chloroethylclonidine-treated tissues. BMY 7378 also had steep and monophasic competition curves and low affinity in all native tissues. In contrast, adrenaline and phenylephrine (in the presence of 100 microM GTP) had monophasic competition curves of low affinity in liver and spleen but biphasic competition curves in cerebral cortex and kidney. Following chloroethylclonidine treatment competition curves for adrenaline, phenylephrine, (+)-niguldipine, SB 216469 and WB 4101 remained biphasic in cerebral cortex and kidney while those for nemonapride remained monophasic. We conclude that alpha1D-adrenoceptors are not readily detectable at the protein level in a variety of rat tissues where their mRNA is expressed. The biphasic competition curves of some agonists and antagonists in chloroethylclonidine-treated rat tissues do not represent alpha1D-adrenoceptors and are not readily explained by the present alpha1A/alpha1B/alpha1D-adrenoceptor classification.

Adrenergic alpha-Agonists↗
PubMed1997

Alpha2-adrenoceptors in opossum kidney cells couple to stimulation of mitogen-activated protein kinase independently of adenylyl cyclase inhibition.

We have compared the effects of adrenaline on activation of mitogen-activated protein kinase (MAP kinase), cyclic AMP accumulation and [3H]thymidine uptake in OK cells, a cell line derived from proximal tubules of the opossum kidney. Effects of serotonin and the direct protein kinase C activator, phorbol-12-myristate-13-acetate (PMA), were also studied. Adrenaline transiently (peak at 5 min, return to baseline by 30 min) and concentration-dependently (EC50 between 10 and 100 nM) stimulated MAP kinase activity. Maximal stimulation was approximately 100% above basal and was similar to the effects of 1 microM serotonin or 1 microM PMA. MAP kinase activation by adrenaline was inhibited by 10 microM phentolamine or 1 microM yohimbine but not significantly affected by 100 nM prazosin or 200 nM pindolol. The selective alpha2-adrenoceptor agonist UK 14,304 (10 microM) also stimulated MAP kinase activity. Activation of the 42 and 44 kDa ERK forms of MAP kinase was demonstrated by immunoblot analysis. The effect of adrenaline and UK 14,304 on MAP kinase was inhibited by pertussis toxin pretreatment and by the MAP kinase kinase inhibitor, PD 98059 (100 microM). Stimulation of MAP kinase activity was independent of cellular cAMP levels and was not affected by protein kinase C downregulation. Adrenaline, UK 14,304, serotonin, and PMA stimulated [3H]thymidine uptake, an effect inhibited by PD 98059. We conclude that adrenaline stimulates MAP kinase activity in OK-cells via alpha2-adrenoceptors and pertussis sensitive G proteins. While this occurs independently of cellular cAMP levels and protein kinase C, it involves the MEKI form of MAP kinase kinase and the ERK forms of MAP kinase. This activation results in enhanced cellular proliferation as assessed by [3H]thymidine uptake.

Adenylate Cyclase Toxin↗
PubMed1997

The Y1 antagonist BIBP 3226 inhibits potentiation of methoxamine-induced vasoconstriction by neuropeptide Y.

We investigated the interaction of neuropeptide Y (NPY) with the alpha 1-adrenoceptor agonist, methoxamine, in control of mean arterial pressure, renovascular resistance and mesenteric vascular resistance in anaesthetized rats. Infusion of 3.0 but not 0.3 microgram/kg/min NPY enhanced the elevations of all three haemodynamic parameters caused by bolus injections of methoxamine (10-100 micrograms/kg). These enhancements largely involved a prolongation of the methoxamine effects. While infusion of the Y1 NPY receptor-selective antagonist, BIBP 3226 (10 micrograms/kg/min), alone did not alter methoxamine-induced vasoconstriction, it inhibited the potentiation by NPY. We conclude that NPY can potentiate methoxamine-induced vasoconstriction in vivo. This is mediated predominantly, if not exclusively, via the Y1 receptor. Endogenously released NPY does not appear to reach sufficient concentrations to cause tonic systemic vasoconstriction or potentiation thereof in the anaesthetized rat.

Animals↗
PubMed1997

A comparison of EMIT and FPIA methods for the detection of cyclosporin A blood levels: does impaired liver function make a difference?

OBJECTIVE: Apparent cyclosporin A (CSA) blood levels, as determined by fluorescence polarization immunoassay (FPIA) and enzyme-multiplied immunoassay technique (EMIT), were compared in CSA-treated patients with various degrees of liver dysfunction. METHODS: FPIA and EMIT were performed in parallel according to test manufacturer instructions in blood from kidney (n = 82), liver (n = 96) and heart transplant (n = 20) patients. RESULTS: The precision of both techniques was greatest in patients with the highest blood levels, and at each blood level greater for the FPIA than for the EMIT. Apparent CSA blood levels, as determined by EMIT, were typically approximately 70% of those determined by FPIA, indicating greater cross-reaction of the antibody in the FPIA with CSA metabolites. However, the ratio of values determined with EMIT and FPIA was very similar in kidney, liver and heart transplant patients. Among liver transplant patients it was also very similar in those without major alterations of hepatic function and in those with impaired excretory (increased bilirubin and gamma GT) or synthetic (i.e., reduced thromboplastin time) function. Extended storage of blood samples for up to 10 days did not affect apparent CSA blood level estimates by EMIT in a clinically relevant manner. CONCLUSIONS: We conclude that the greater specificity of the antibody in the EMIT for the CSA parent compound does not translate into a clinically relevant advantage for CSA monitoring.

Cyclosporine↗
PubMed1997

Renovascular and tubular effects of neuropeptide Y are discriminated by PP56 (D-myo-inositol 1,2,6-triphosphate) in anaesthetized rats.

Systemic infusion of neuropeptide Y (NPY; 1 microg kg-1 min-1) for 120 min rapidly reduced renal blood flow and increased mean arterial pressure and renovascular resistance and, at later time points (> 30 min), enhanced diuresis, natriuresis and calciuresis in anaesthetized rats. Infusion of the reported NPY antagonist PP56 (D-myo-inositol 1,2,6-triphosphate, 333 mg kg-1 min-1) slightly but significantly enhanced renal blood flow and reduced renovascular resistance over the course of the infusion period. Infusion of PP56 together with NPY (starting 30 min prior to the NPY infusion) significantly inhibited NPY-induced alterations of mean arterial pressure, renal blood flow and renovascular resistance. Coinfusion of PP56 also attenuated the renovascular effects of bolus injections of NPY (0.1-10 microg/kg) but at the highest NPY dose the antagonistic effect of PP56 could partially be overcome. In contrast to the antagonism of the vascular NPY effects, infusion of PP56 did not significantly affect NPY-induced enhancements of diuresis, natriuresis and calciuresis. Thus, PP56 is a surmountable antagonist of vascular but not tubular NPY effects. We conclude that tubular NPY effects occur largely independently of alterations of renal haemodynamics.

Anesthesia↗
PubMed1997

Protein kinase C isoenzymes in rat and human cardiovascular tissues.

1. We have compared the expression of protein kinase C (PKC) activity and immuno-detectable isoenzymes in cytosolic and membrane extracts of rat and human cardiovascular tissues (heart, kidney, aorta, saphenous vein). Experiments were performed in raw extracts and upon combined diethylaminoethylcellulose (DEAE) and phenylsepharose column chromatography. 2. PKC activity that bound to DEAE mostly eluted with 200 mM NaCl. DEAE-purified PKC from all tissues except rat kidney bound almost quantitatively to phenylsepharose and eluted with 0.5-0 M NaCl. 3. Immunoblots with an antibody against classical PKCs and the activator profile for phosphatidylserine, diolein and Ca2+ revealed that the PKC from rat kidney, which did not bind to phenylsepharose, was most probably due to a proteolytically-generated, constitutively active PKC which is not under the control of a regulatory subunit. 4. Studies in the reference tissue, rat brain, demonstrated that all PKC isoenzymes investigated (classical PKCs alpha, beta, gamma, new PKCs delta, epsilon, eta, theta, and atypical PKCs zeta, lambda, iota) have similar DEAE and phenylsepharose chromatography elution profiles. In the functional assay an inhibitor of all known PKC isoenzymes, bisindolylmaleimide, and a specific inhibitor of classical PKCs, Gö 6976, both inhibited PKC from rat brain completely and with high potency indicating that the functional assay preferentially detects classical PKC isoenzymes. 5. Each PKC isoenzyme had a tissue-specific expression profile which was similar in rat and man. The classical PKC alpha, the new PKCs delta and epsilon and all atypical PKCs were detectable in most tissues, whereas the PKC beta and PKC gamma were not detected in any pheripheral tissue; PKC eta and PKC theta were found in some tissues. 6. We conclude that combined DEAE and phenylsepharose chromatography is useful to enrich and detect PKC isoenzymes; no major species differences in tissues-specific expression patterns appear to exist between rat and man.

Animals↗