Fetal cerebrovascular impedance is reduced in left congenital diaphragmatic hernia.

OBJECTIVES: Congenital diaphragmatic hernia (CDH) can cause a significant mass effect in the fetal thorax, displacing the heart into the opposite hemithorax. In left-sided CDH (L-CDH), this is associated with smaller left-sided cardiac structures and reduced left-ventricular cardiac output (LVCO). The effect of these physiologic changes on cerebral blood flow is not well understood. We sought to describe the middle cerebral artery (MCA) pulsatility index (PI), a measure of cerebrovascular impedance, in fetuses with L-CDH and those with right-sided CDH (R-CDH) compared with unaffected fetuses, and the relationship between MCA-PI and LVCO. We hypothesized that MCA-PI would be lower in fetuses with L-CDH and similar in those with R-CDH compared to controls, and that MCA-PI would be correlated with LVCO. METHODS: We identified all fetuses with CDH evaluated at The University of California San Francisco, San Francisco, CA, USA from 2011 to 2018. Fetal echocardiograms and ultrasound scans were reviewed. Umbilical artery and MCA Doppler examinations were assessed to calculate pulsatility indices. Ventricular outputs were calculated using Doppler-derived stroke volume and fetal heart rate. Lung-to-head ratio (LHR), estimated fetal weight, biparietal diameter (BPD) and head circumference (HC) were obtained from fetal sonograms. Measurements in fetuses with CDH, according to the side of the defect, were compared with those in unaffected, gestational age-matched controls. A subset of CDH survivors had available data on neurodevelopmental outcome, as assessed using the Bayley Scales of Infant Development, 3rd edition. RESULTS: A total of 64 fetuses with CDH (L-CDH, n = 53; R-CDH, n = 11) comprised the study groups, with 27 unaffected fetuses serving as controls. Mean gestational age at evaluation was similar between the three groups. Compared to controls, fetuses with L-CDH had significantly lower LVCO expressed as a percentage of combined cardiac output (CCO) (32%; 95% CI, 29-35% vs 38%; 95% CI, 33-42%; P = 0.04) and lower MCA-PI Z-score (-1.3; 95% CI, -1.7 to -1.0 vs 0.08; 95% CI, -0.5 to 0.6; P < 0.001), while they did not differ between the R-CDH group and controls. There was a strong positive association between LVCO as a percentage of CCO and MCA-PI Z-score in the overall cohort of CDH and control fetuses (P = 0.01). BPD and HC were similar between the three groups. At neurodevelopmental follow-up, mean cognitive, motor and language scores in the CDH group were within 1 SD of those in the general population. CONCLUSION: MCA-PI values are significantly lower in fetuses with L-CDH as compared to controls, and lower LVCO was correlated with lower MCA vascular impedance. The neurodevelopmental effect of changes in MCA-PI in response to decreased LVCO is unknown, although, on average, CDH survivors had neurodevelopmental scores in the normal range. This may reflect a fetal compensatory mechanism in response to diminished antegrade cerebral blood flow. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Hidden autoantibodies against common serum proteins in murine systemic lupus erythematosus. Detection by in vitro plaque-forming cell assay.

The autoantibodies found in human and murine systemic lupus erythematosus (SLE) are generally directed against cells or components of cells such as nuclear antigens. This predilection may be due to the unusual immunogenicity of certain autoantigens, or to unusual patterns of antibody crossreactivity. Alternatively, the observed spectrum of reactivities may reflect the in vivo absorption of those autoantibodies directed against soluble antigens. To test whether hitherto undetected autoantibodies against serum proteins might exist in murine SLE, we developed assays that were independent of the possibility of absorption of autoantibodies by serum autoantigens; large numbers of plaque-forming cells (PFC) directed against mouse albumin and mouse transferrin were easily detected in the spleens of MRL/Mp-lpr/lpr, BXSB, and NZB mice. The secreted antibodies were relatively specific for the mouse proteins, since only limited cross-reactivity was seen with albumin and transferrins of other species in inhibition experiments. The production of these hidden antibodies could not be the result of diffuse polyclonal B cell activation, since the PFC to mouse transferrins and albumin were not always accompanied by comparable numbers of PFC against related albumins and transferrins. The results indicate that autoantibody production in murine lupus is a generalized phenomenon, not limited to the production of autoantibodies to nuclear or other cell-bound antibodies. However, the relative specificity of the autoantibodies for self-antigens indicates that diffuse polyclonal B cell activation cannot be the mechanism responsible, and argues that a selective mechanism, probably driven by antigen, accounts for production of autoantibodies in SLE.

Antigen nonspecific effect of major histocompatibility complex haplotype on autoantibody levels in systemic lupus erythematosus-prone lpr mice.

MHC-linked genes strongly influence susceptibility to autoimmune diseases and also regulate responses to exogenous antigens. To begin to understand the mechanism of this MHC effect on disease, we have investigated MHC-congenic mouse strains that develop spontaneous autoimmunity because of the lpr gene. C57BL6/lpr (B6/lpr) mice (H-2b) are known to have substantial levels of autoantibodies to chromatin, single stranded DNA (ssDNA3), and IgG of different murine subclasses (rheumatoid factor). We have crossed the H-2d and the H-2bm12 (la mutant) haplotypes onto the B6/lpr background. Surprisingly, levels of all the autoantibodies were markedly lower in B6/lpr.H-2d, but levels in B6/lpr.H-2bm12 were no different from those in B6/lpr mice. The downregulating influence of the H-2d allele was dominant, and there was no effect on autoantibody fine specificities. The genetics of the H-2d effect and its diffuse influence on multiple autoantibody specificities, in addition to the lack of effect of the bm12 mutation, which modifies the peptide-binding groove of I-A, together raise the question of whether MHC-linked genes other than classical (IR) genes may be responsible for MHC disease associations in this model.

Antioxidant capacity is correlated with steroidogenic status of the corpus luteum during the bovine estrous cycle.

The reactions of steroid hormone biosynthesis are accompanied by formation of oxygen radicals. We determined the levels of some antioxidants and antioxidative enzymes at different developmental stages of bovine corpora lutea to examine their correlation with steroidogenic status. Plasma progesterone concentrations of estrous cycle synchronized cows increased until day 16, and then decreased rapidly during luteal regression. The levels of steroidogenic cytochrome P450scc and adrenodoxin paralleled the changes in plasma progesterone. Among the antioxidative enzymes examined, the SOD and catalase activities showed patterns most similar to plasma progesterone. Catalase and SOD activities increased 6-8 fold from day 6 to 16 of the estrous cycle and then decreased during the luteal regression. Ascorbate and beta-carotene showed low but significant correlation with P450scc and plasma progesterone levels. The profiles of two lipophilic antioxidants in corpora lutea were very different. beta-carotene concentration increased by approximately 6 fold from day 6 to 16, and decreased in regressive tissue. alpha-tocopherol showed a 3 fold increase between days 6 and 9 followed by a rapid decrease. Thus, at the peak of steroidogenesis at mid-luteal phase alpha-tocopherol levels decreased, but beta-carotene levels increased. The correlation between the levels of some antioxidant enzymes and compounds with progesterone levels indicates that antioxidative mechanisms are activated to cope with steroidogenesis dependent oxyradical formation in the bovine corpus luteum.

Atriopeptin II elevates cyclic GMP, activates cyclic GMP-dependent protein kinase and causes relaxation in rat thoracic aorta.

Synthetic atriopeptin II, an atrial natriuretic factor with potent vasodilatory effects, was studied in isolated strips of rat thoracic aorta to determine its actions on contractility, cyclic nucleotide concentrations and endogenous activity of cyclic nucleotide-dependent protein kinases. Atriopeptin II was found to relax aortic strips precontracted with 0.3 microM norepinephrine whether or not the endothelial layer was present. Relaxation to atriopeptin II was closely correlated in a time- and concentration-dependent manner with increases in cyclic GMP concentrations and activation of cyclic GMP-dependent protein kinase (cyclic GMP-kinase). The threshold concentration for all three effects was 1 nM. Atriopeptin II (10 nM for 10 min) produced an 80% relaxation, an 8-fold increase in cyclic GMP concentrations and a 2-fold increase in cyclic GMP-kinase activity ratios. Atriopeptin II did not significantly alter cyclic AMP concentrations or cyclic AMP-dependent protein kinase activity. These data suggest that cyclic GMP and cyclic GMP-kinase may mediate vascular relaxation to a new class of vasoactive agents, the atrial natriuretic factors. Similar effects have been observed with the nitrovasodilator, sodium nitroprusside, and the endothelium-dependent vasodilator, acetylcholine. Therefore, a common biochemical mechanism of action that includes cyclic GMP accumulation and activation of cyclic GMP-kinase may be involved in vascular relaxation to nitrovasodilators, endothelium-dependent vasodilators and atrial natriuretic factors.

Effects of atriopeptin on particulate guanylate cyclase from rat adrenal.

Atriopeptin II activated particulate guanylate cyclase 5-10-fold in a concentration- and time-dependent fashion in crude membranes obtained from homogenates of rat adrenal cortex or medulla. Similar effects were observed with other atriopeptin analogs. Soluble guanylate cyclase and adenylate cyclase in these preparations were not activated. Accumulation of cyclic GMP in minces of adrenal cortex or medulla was increased 6-8-fold due to atriopeptin II activation of particulate guanylate cyclase. Several thiol-reactive agents blocked the activation of particulate guanylate cyclase, suggesting that free thiol groups on membrane proteins may be important in atriopeptin receptor-guanylate cyclase coupling.

Regulation of particulate guanylate cyclase by atriopeptins: relation between peptide structure, receptor binding, and enzyme kinetics.

Structural analogs of atriopeptins (APs) were compared for their ability to activate particulate guanylate cyclase and bind to specific receptors in rat adrenal membranes. All analogs tested increase Vmax without altering the concentration of substrate required for half-maximum activity or the positive coperativity exhibited by the enzyme. Maximum velocities (pmoles of cGMP produced per min per mg protein) achieved in the absence and presence of APs were 128.3 +/- 6.6 and 283.8 +/- 20.6 using Mn2+-GTP, and 53.7 +/- 3.7 and 149.9 +/- 7.6 using Mg2+-GTP as the substrate, respectively. Although all APs were equally efficacious in activating the enzyme, their rank potency was ANF (8-33) = AP III = AP II greater than AP I when either divalent cation was used as the cofactor. The EC50 for activation of guanylate cyclase by AP I was about 10(-7) M, while that for the other peptides was about 10(-8) M, using either divalent cation cofactor. 125I-labeled ANF bound to rat adrenal membranes with a KD of 5.10(-10) M. Although all APs were equally efficacious in competing with labeled ANF for receptor binding, their rank potency was identical to that for enzyme activation. The Ki for AP I was about 10(-8) M, while that for the other peptides was about 10(-10) M. These data suggest that the carboxy terminal Phe-Arg present in the AP analogs except AP I and critical for biological and receptor-binding activity are also important in coupling receptor-ligand interaction with guanylate cyclase activation. The correlation between the rank order potency for receptor binding, enzyme activation, and the reported physiological actions of APs support the suggestion of a functional coupling between these proteins.

Around-the-clock, controlled-release oxycodone therapy for osteoarthritis-related pain: placebo-controlled trial and long-term evaluation.

BACKGROUND: Although opioid analgesics have well-defined efficacy and safety in treatment of chronic cancer pain, further research is needed to define their role in treatment of chronic noncancer pain. OBJECTIVE: To evaluate the effects of controlled-release oxycodone (OxyContin tablets) treatment on pain and function and its safety vs placebo and in long-term use in patients with moderate to severe osteoarthritis pain. METHODS: One hundred thirty-three patients experiencing persistent osteoarthritis-related pain for at least 1 month were randomized to double-blind treatment with placebo (n = 45) or 10 mg (n = 44) or 20 mg (n = 44) of controlled-release oxycodone every 12 hours for 14 days. One hundred six patients enrolled in an open-label, 6-month extension trial; treatment for an additional 12 months was optional. RESULTS: Use of controlled-release oxycodone, 20 mg, was superior (P<.05) to placebo in reducing pain intensity and the interference of pain with mood, sleep, and enjoyment of life. During long-term treatment, the mean dose remained stable at approximately 40 mg/d after titration, and pain intensity was stable. Fifty-eight patients completed 6 months of treatment, 41 completed 12 months, and 15 completed 18 months. Common opioid side effects were reported, several of which decreased in duration as therapy continued. CONCLUSIONS: Around-the-clock controlled-release oxycodone therapy seemed to be effective and safe for patients with chronic, moderate to severe, osteo-arthritis-related pain. Effective analgesia was accompanied by a reduction in the interference of pain with mood, sleep, and enjoyment of life. Analgesia was maintained during long-term treatment, and the daily dose remained stable after titration. Typical opioid side effects were reported during short- and long-term therapy.

Role of prostaglandins in acetylcholine-induced contraction of aorta from spontaneously hypertensive and Wistar-Kyoto rats.

Evidence in support of prostaglandin (PG) H2 as the endothelium-derived contracting factor released in response to acetylcholine in vessels from adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) is to a large degree indirect. Therefore, the purpose of the present study was to test the hypothesis that a prostaglandin or prostaglandins other than PGH2 may serve as the endothelium-derived contracting factor that mediates acetylcholine-induced contraction in these vessels. Acetylcholine-induced contraction of endothelium-intact aorta from 7- to 12-month-old SHR and WKY in the presence of the nitric oxide synthase inhibitor N omega-nitro-L-arginine was abolished by indomethacin and only partially decreased by the thromboxane (Tx) A2/PGH2 receptor antagonist SQ29548. Contraction induced by the TxA2/ PGH2 receptor agonist U46619 was abolished by SQ29548. These findings suggest that in endothelium-intact aorta from SHR and WKY, acetylcholine causes the release of a cyclooxygenase product other than PGH2 that induces contraction independently of TxA2/PGH2 receptor activation. To investigate which prostaglandin or prostaglandins could be responsible for the TxA2/PGH2 receptor-independent component, we challenged endothelium-denuded aorta from SHR and WKY with various prostaglandins in the presence of SQ29548. In SQ29548-treated aorta from 7- to 12-month-old rats, maximal contractions to PGF2 alpha, PGE2, and carbacyclin (a PGI2 analogue) were greater than the magnitude of acetylcholine-induced contraction. These findings suggest that PGF2 alpha, PGE2, and/or PGI2 could serve as mediators of the TxA2 receptor-independent component of the acetylcholine-induced contraction. However, in studies with SQ29548-treated aorta from 4- to 6-week-old SHR and WKY (an age at which acetylcholine-induced contraction is known to be absent), maximal contraction to PGF2 alpha and PGE2 was also greater or equivalent to that of SQ29548-treated aorta from 7- to 12-month-old rats, whereas carbacyclin induced negligible contraction. Thus, unlike PGE2 and PGF2 alpha, the age-dependent pattern of contraction induced by carbacyclin closely resembles the pattern induced by acetylcholine. We also measured the levels of PGI2 released in response to acetylcholine and found that they are sufficient to account for the TxA2 receptor-independent component of the acetylcholine-induced contraction. Thus, we propose that PGI2 released in response to acetylcholine may serve as the endothelium-derived contracting factor that elicits the TxA2/PGH2 receptor-independent and dependent components of the acetylcholine-induced contraction.

Increased CSF volumes are associated with diminished subjective responses to cocaine infusion.

We evaluated the hypothesis that ventricular and cortical CSF volume increases are associated with reductions in the magnitude of euphoric effects produced by intravenous IV cocaine infusion in cocaine dependent (CD) individuals. Eleven CD patients participating in a cocaine-infusion study and eleven control subjects underwent magnetic resonance imaging (MRI). Two CSF regions of interest (lateral ventricles and frontal cortex CSF) and two comparison regions (third ventricle and posterior cortex CSF) were measured. Self-reported ratings of the intensity of euphoric response ("high") were obtained from the CD subjects at 3, 10, and 30 minutes after IV administration of cocaine. A significant negative correlation was observed between the volume of the lateral ventricles and subjective ratings of the "high" experienced at 3 minutes, but not at 10 and 30 minutes after cocaine infusion. In contrast, a significant negative correlation between frontal cortex CSF volume and the intensity of euphoric response was observed at 30 minutes after IV cocaine. No significant associations were observed between the volumes of the two comparison regions and any subjective ratings of "high." No significant volume differences were observed between the CD and control groups in any region. The results suggest larger lateral ventricular volumes are associated with a decrease in immediate euphoria while larger frontal cortex CSF volumes are associated with a decrease in the duration of the euphoria induced by cocaine infusion. The age-related brain volume reductions underlying the volume increase in these two CSF spaces may be the neurobiological basis of the age-related reduction in the rates of addiction.

Cutaneous vascular immunofluorescence in rheumatoid arthritis. Correlation with circulating immune complexes and vasculitis.

The presence of immunoglobulin and complement in the cutaneous blood vessels of clinically uninvolved forearm skin was studied in 70 patients with rheumatoid arthritis, using immunofluorescent techniques. Patients with evidence of these immune deposits had a greater prevalence of circulating immune complexes, vasculitic skin lesions, subcutaneous nodules, high titer rheumatoid factor and other findings suggestive of active vasculitis. Biopsy of uninvolved forearm skin may be a useful tool in assessing those patients with rheumatoid arthritis suspected of having a systemic vasculitis.

Desensitization to nitroglycerin in vascular smooth muscle from rat and human.

Guanylate cyclase in high speed supernatant fractions obtained from rat thoracic aorta or human coronary arteries pretreated with nitroglycerin exhibited a marked desensitization to activation by nitroglycerin, nitroprusside, and nitric oxide. However, activation of soluble guanylate cyclase by arachidonic acid was unaffected by pretreatment of vessels with nitroglycerin. Furthermore, activation of soluble guanylate cyclase by protoporphyrin IX was increased 4-fold when vessels were pretreated with nitroglycerin. Soluble guanylate cyclase partially purified from nitroglycerin-pretreated rat thoracic aorta by immunoprecipitation with a specific monoclonal antibody exhibited persistent desensitization to nitrate-induced activation. These data suggest that nitroglycerin-induced desensitization of guanylate cyclase to activation by nitrovasodilators represents a stable alteration of the enzyme. In contrast, activation by protoporphyrin IX of guanylate cyclase immunoprecipitated from nitroglycerin-pretreated or control vessels was not significantly different. This suggests that the mechanism of protoporphyrin activation of guanylate cyclase is different than the mechanism with nitrovasodilators. Activation of particulate guanylate cyclase by Lubrol-PX, hemin, or atrial natriuretic factor was not significantly different with enzyme prepared from nitroglycerin-pretreated or control vessels from rat and human. Thus, nitroglycerin-induced desensitization of rat thoracic aorta or human coronary artery results in a relatively stable molecular alteration of soluble guanylate cyclase such that the enzyme is specifically less sensitive to activation by nitrovasodilators whereas the effects of other activators of the enzyme are either unchanged or increased.

Inhibition of early events in the human T-lymphocyte response to mitogens and alloantigens by hydrogen peroxide.

Hydrogen peroxide (100 to 200 microM) inhibited the response of human peripheral-blood mononuclear cells (PBMCs) in phytohemagglutinin, concanavalin A, and mixed lymphocyte culture assays by more than 90% without affecting cell viability. The response of PBMCs to pokeweed mitogen was stimulated twofold by 50 microM H2O2, but 200 microM H2O2 inhibited the pokeweed mitogen response by more than 95%. A 50 microM concentration of H2O2 completely blocked the generation of cytotoxic T cells in the mixed lymphocyte culture but did not inhibit the production of interleukin 2. Concentrations of 100 microM to 200 microM H2O2 inhibited interleukin 2 production by 45% to 57%. The H2O2 appeared to block early events in T-cell activation, since 200 microM H2O2 was not inhibitory when added one hour after stimulating the cells with phytohemagglutinin. Treatment of PBMCs with 200 microM H2O2 did not decrease the total cellular thiol pool, suggesting that H2O2-mediated inhibition of the proliferative response was not due to thiol oxidation. However, pretreatment of PBMCs with the lipid antioxidants butylated hydroxyanisole, butylated hydroxytoluene, and n-propyl gallate blocked more than 75% of the inhibitory effect of H2O2, suggesting that H2O2 inhibits T-cell activation by inducing lipid peroxidation.

Hydrogen peroxide-mediated inhibition of T-cell response to mitogens is a result of direct action on T cells.

Hydrogen peroxide, a reactive oxygen intermediate produced by activated neutrophils, has been shown to inhibit the response of human T lymphocytes to mitogens and alloantigens. Since hydrogen peroxide is known to react with iron and to induce lipid peroxidation, we compared the effects of hydrogen peroxide and a lipid peroxidation product, malondialdehyde, on the response of human peripheral blood mononuclear cells to T-cell mitogens. Peripheral blood mononuclear cells pretreated with 1 mmol/L of malondialdehyde, washed, and resuspended in fresh medium exhibited no inhibition of phytohemagglutinin responsiveness. Peripheral blood mononuclear cells treated in the same manner but with 200 mumol/L of hydrogen peroxide were inhibited by more than 95%. The addition of ferric edetate did not alter the inhibitory effects of 50 to 100 mumol/L of hydrogen peroxide, nor did the addition of deferoxamine, an iron chelator. These studies suggest that exogenous lipid peroxidation does not affect lymphocyte activation but that hydrogen peroxide has a direct inhibitory effect. Although monocytes are necessary for T-cell mitogenic responses, the effect of hydrogen peroxide was found to be directed at T lymphocytes. Exposure of T cells to a single dose of 200 mumol/L of hydrogen peroxide resulted in more than 71% suppression of the proliferative response measured 48 hours later, but the effect was spontaneously reversed by 72 to 96 hours. Repeated exposure of the cells to hydrogen peroxide resulted in continued inhibition of the proliferative response. These findings suggest that hydrogen peroxide produced by inflammatory phagocytic cells might be capable of suppressing the immune response of nearby T lymphocytes.

Potentiation of norepinephrine-induced contraction by primary prostaglandin receptor activation in rat aorta.

This study investigates the role of primary prostaglandin receptor activation in the modulation of agonist-induced vascular smooth muscle contraction. Prostaglandin F2 alpha induced a concentration-dependent contraction of the rat aorta that was nearly abolished by the thromboxane A2 receptor antagonist, SQ29548. Prostaglandin F2 alpha in the presence of SQ29548 induced leftward shifts of the norepinephrine and KCl concentration-response curves. Nifedipine abolished the leftward shift of the norepinephrine concentration-response curve observed in the presence of prostaglandin F2 alpha and SQ29548. These results suggest that a function of primary prostaglandin receptor activation may be to potentiate agonist-induced contraction. The potentiation is dependent upon the opening of dihydropyridine-sensitive Ca2+ channels.

Norepinephrine-induced phosphatidylcholine hydrolysis in intact rat aorta.

The present study tests whether norepinephrine induces the hydrolysis of phosphatidylcholine (PC) in intact vascular smooth muscle. Norepinephrine and the phorbol ester, phorbol myristate acetate (PMA), increased the formation of choline and phosphorylcholine in rat aorta. The norepinephrine-induced PC hydrolysis was inhibited by the protein kinase C (PKC) antagonist, 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H7). These results suggest that the diacylglycerol formed during the sustained phase of the contractile response to norepinephrine may be derived, at least in part, from PC hydrolysis. The hydrolysis may be mediated through PKC activation of phospholipase C and D.

Effect of cyanide on nitrovasodilator-induced relaxation, cyclic GMP accumulation and guanylate cyclase activation in rat aorta.

The effects of sodium cyanide on relaxation, increases in cyclic GMP accumulation and guanylate cyclase activation induced by sodium nitroprusside and other nitrovasodilators were examined in rat thoracic aorta. Cyanide abolished nitroprusside-induced relaxation and the associated increase in cyclic GMP levels. Basal levels of cyclic GMP and cyclic AMP were also depressed. Reversal of nitroprusside-induced relaxation by cyanide was independent of the tissue level of cyclic GMP prior to addition of cyanide. Incubation of nitroprusside with cyanide prior to addition to aortic strips did not alter the relaxant effect of nitroprusside. Sodium azide-, hydroxylamine-, N-methyl-N'-nitro-N-nitrosoguanide-, nitroglycerin- and acetylcholine-induced relaxations and increased levels of cyclic GMP were also inhibited by cyanide. Relaxations induced by nitric oxide were also inhibited by cyanide, although the relaxation with the low concentration of nitric oxide employed was not accompanied by detectable increases in cyclic GMP. Relaxation to 8-bromo-cyclic GMP was essentially unaltered by cyanide; however, isoproterenol-induced relaxation was inhibited. Guanylate cyclase in soluble and particulate fractions of aorta homogenates was activated by nitroprusside and the activation was prevented by cyanide. The present results suggest that cyanide inhibits nitrovasodilator-induced relaxation through inhibition of guanylate cyclase activation; however, cyanide may also have nonspecific effects which inhibit relaxation.

Effects of protein kinase C activation on norepinephrine-induced phosphatidylinositide hydrolysis in intact rat aorta.

The purpose of this study was to investigate the role of protein kinase C in the regulation of alpha 1-adrenoceptor-mediated phosphatidylinositide hydrolysis in intact vascular smooth muscle. Phorbol myristate acetate (0.1 and 1 microM) and staurosporine inhibited and potentiated, respectively, norepinephrine-induced inositol phosphate formation in intact rat aorta. In contrast, 30 microM prostaglandin F2 alpha, which activated protein kinase C to a similar magnitude as 1 microM phorbol myristate acetate, was without effect on norepinephrine-induced inositol phosphate formation. These results suggest that protein kinase C activated in response to physiologic agonists, but not in response to phorbol esters, may be compartmentalized within the smooth muscle cell.

Time course of phorbol ester-induced contraction and protein kinase C activation in rat aorta.

This study investigates the relationship between the rate of phorbol ester-induced contraction of intact rat aorta and protein kinase C activation, as assessed by the translocation of protein kinase C from the cytosolic to the particulate fraction. Aorta was exposed to Ca(2+)-free physiologic salt solution prior to phorbol ester to prevent Ca(2+)-induced protein kinase C translocation during tissue homogenization. Phorbol myristate acetate, as well as phorbol dibutyrate, decreased cytosolic and/or increased particulate protein kinase C activity as early as 5 s following phorbol ester addition, which was prior to, or coincident with, the onset of contraction. These results suggests that phorbol ester-induced contraction of intact vascular smooth muscle is associated in a time-dependent manner with protein kinase C activation.

Endothelin ETA and ETB receptors in subarachnoid hemorrhage-induced cerebral vasospasm.

The relative roles of endothelin ETA and ETB receptor activation in cerebral vasospasm following subarachnoid hemorrhage were investigated in the rabbit. The endothelin ETA receptor antagonist, BQ610 (1 microM; homopiperidinyl-CO-Leu-D-Trp(CHO)-D-Trp-OH), and the endothelin ETA/ETB receptor antagonist, PD145065 (1 microM; Ac-D-Bhg-L-Leu-L-Asp-L-Ile-L-Ile-L-Trp), relaxed the vasospastic basilar artery in situ by 45% and 87%, respectively. These results suggest that subarachnoid hemorrhage-induced vasospasm of the rabbit basilar artery is due to activation of both endothelin ETA and ETB receptors.