Effect of subarachnoid hemorrhage on dilatation of rat basilar artery in vivo

1996 ◽  
Vol 271 (1) ◽  
pp. H126-H132 ◽  
Author(s):  
C. G. Sobey ◽  
D. D. Heistad ◽  
F. M. Faraci
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Guanylate Cyclase ◽  
Basilar Artery ◽  
Soluble Guanylate Cyclase ◽  
Autologous Blood ◽  
K Channels ◽  
Cyclic Monophosphate ◽  
Calcitonin Gene ◽  
Cerebral Vasodilator

Cerebral vasodilator responses are often impaired following subarachnoid hemorrhage (SAH). Because depolarization of vascular muscle may occur after SAH, we tested in vivo the hypothesis that SAH may augment dilatation in response to hyperpolarization due to activation of K+ channels. Anesthetized rats were studied two days after injection of saline or autologous blood into the cisterna magna. Diameter of the basilar artery in vivo was 224 +/- 5 microns (mean +/- SE) in saline-treated rats and 201 +/- 6 microns in SAH rats (P < 0.05). In control rats, acetylcholine (ACh), sodium nitroprusside (SNP), aprikalim and calcitonin gene-related peptide (CGRP; both activators of ATP-sensitive K+ channels), papaverine, 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP), and brain natriuretic peptide (BNP; an activator of particulate guanylate cyclase) produced concentration-dependent dilatation. In SAH rats, vasodilatation was impaired in response to ACh and SNP. In contrast, vasodilator responses to aprikalim and CGRP were augmented in SAH, rats (by two- to fourfold). Vasodilator responses to 8-BrcGMP, papaverine, and BNP were similar in both groups. Thus responses mediated by activation of soluble guanylate cyclase are selectively impaired by SAH, but responses to guanosine 3',5'-cyclic monophosphate are normal. Vasodilator responses to activation of ATP-sensitive K+ channels are augmented by SAH.

Impaired cerebral vasodilator responses to NO and PDE V inhibition after subarachnoid hemorrhage

1999 ◽  
Vol 277 (5) ◽  
pp. H1718-H1724 ◽  
Author(s):  
Christopher G. Sobey ◽  
Lilly Quan
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Basilar Artery ◽  
Soluble Guanylate Cyclase ◽  
Autologous Blood ◽  
Cranial Window ◽  
Low Concentrations ◽  
Cerebral Vasodilatation ◽  
Hydrolysis Of ◽  
Cerebral Vasodilator

Subarachnoid hemorrhage (SAH) is associated with impaired nitric oxide (NO)-mediated cerebral vasodilatation. We tested the hypothesis that SAH causes alterations in the production of, hydrolysis of, or responsiveness to cGMP in the rat basilar artery in vivo. Rats were injected with saline or autologous blood into the cisterna magna. Two days later, effects of vasoactive drugs on basilar artery diameter were examined using a cranial window preparation. Vasodilator responses to ACh, sodium nitroprusside (SNP), and low concentrations (≤10−5 M) of zaprinast, an inhibitor of phosphodiesterase V (PDE V), were impaired in SAH rats ( P < 0.05). In contrast, vasodilator responses to adenosine and 8-BrcGMP were similar in control and SAH rats. Vasoconstrictor responses to 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase, were unaffected by SAH. In the presence of zaprinast (10−5–10−4 M), responses to ACh and SNP were equivalent in control and SAH rats. Thus an increased rate of cGMP hydrolysis by PDE V may be a major factor contributing to the impairment of NO-mediated cerebral vasodilatation after SAH.

Effects of the Ca++-permeable nonselective cation channel blocker LOE 908 on subarachnoid hemorrhage—induced vasospasm in the basilar artery in rabbits

2003 ◽  
Vol 98 (3) ◽  
pp. 561-564 ◽  
Author(s):  
Yoshifumi Kawanabe ◽  
Tomoh Masaki ◽  
Nobuo Hashimoto
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Intravenous Administration ◽  
Basilar Artery ◽  
Channel Blocker ◽  
Autologous Blood ◽  
Content Type ◽  
Dependent Part ◽  
Before And After ◽  
Fine Print

Object. The Ca++ influx into vascular smooth-muscle cells (VSMCs) plays a fundamental role in the development and chronic effects of vasospasm after subarachnoid hemorrhage (SAH). The Ca++-permeable nonselective cation channels (NSCCs) are activated by several endothelium-derived constricting factors such as endothelin 1 (ET-1) and thromboxane A2. Moreover, the receptor-operated Ca++ channel blocker LOE 908 inhibits ET-1—induced extracellular Ca++ influx via NSCCs in the VSMCs of the basilar artery (BA) and the NSCC-dependent part of ET-1—induced vasoconstriction of BA rings. The purpose of the present study was to evaluate the in vivo role of LOE 908 on SAH-induced vasospasm. Methods. Forty-two Japanese white rabbits were assigned to seven groups. Treatment groups consisted of the following: 1) control rabbits without SAH that received a cisternal injection of saline; 2) rabbits with SAH that were subjected to the intravenous administration of saline; 3 through 6) rabbits with SAH that underwent the intravenous administration of 0.01, 0.1, 1, or 10 mg/kg LOE 908, respectively; and 7) rabbits without SAH that underwent the intravenous administration of 10 mg/kg LOE 908. Autologous blood was injected into the cisterna magna. The caliber of the BA was measured on angiographic studies before and after the cisternal injection of autologous blood. The intravenous injection of LOE 908 inhibited the magnitude of an SAH-induced vasosapsm. In addition, the concentration of LOE 908 required to relax vasospasm (1 mg/kg) correlated with that required to block Ca++ influx into VSMCs. Conclusions. The Ca++ channel blocker LOE 908 may inhibit the magnitude of an SAH-induced vasospasm by blocking the influx of Ca++ through NSCCs in rabbit BAs. Blocking the NSCCs may represent a new treatment for cerebral vasospasm after SAH.

Role of ATP-sensitive K+ channels in CGRP-induced dilatation of basilar artery in vivo

1993 ◽  
Vol 265 (2) ◽  
pp. H581-H585 ◽  
Author(s):  
T. Kitazono ◽  
D. D. Heistad ◽  
F. M. Faraci
Keyword(s):  
Basilar Artery ◽  
Minor Component ◽  
K Channels ◽  
Cranial Window ◽  
Calcitonin Gene ◽  
A Minor ◽  
Oxide Synthase ◽  
Camp Levels

Stimulation of adenylate cyclase appears to activate ATP-sensitive K+ channels in the basilar artery. We tested the hypothesis that calcitonin gene-related peptide (CGRP), which increases intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels, activates ATP-sensitive K+ channels and thereby causes vasodilatation. Using a cranial window in anesthetized rats, we examined responses of the basilar artery to CGRP in vivo. We also examined responses of the artery to another vasoactive peptide, vasoactive intestinal peptide (VIP). Topical application of CGRP (10(-11) to 10(-8) M) increased diameter of the basilar artery. Responses of the basilar artery to CGRP were almost abolished by a CGRP1 receptor antagonist, CGRP-(8-37). Vasodilatation in response to VIP was much smaller than that produced by CGRP. Dilator responses of the basilar artery to 10(-9) and 10(-8) M CGRP were inhibited by glibenclamide (10(-6) M), a selective inhibitor of ATP-sensitive K+ channels, by 69 +/- 19 and 41 +/- 9%, respectively. NG-nitro-L-arginine methyl ester (10(-5) M), an inhibitor of nitric oxide synthase, did not attenuate dilator response to 10(-8) M CGRP but inhibited responses to 10(-9) M CGRP by 34 +/- 12%. Indomethacin did not alter dilator responses to CGRP. These findings suggest that a minor component of CGRP-induced dilatation of the basilar artery is mediated by endothelium-derived relaxing factor. Vasodilatation in response to CGRP appears to be mediated primarily by direct activation of CGRP1 receptors on vascular muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide synthase and guanylate cyclase levels in canine basilar artery after subarachnoid hemorrhage

1995 ◽  
Vol 82 (2) ◽  
pp. 250-255 ◽  
Author(s):  
Hidetoshi Kasuya ◽  
Bryce K. A. Weir ◽  
Masaki Nakane ◽  
Jennifer S. Pollock ◽  
Lydia Johns ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Subarachnoid Hemorrhage ◽  
Guanylate Cyclase ◽  
Basilar Artery ◽  
Soluble Guanylate Cyclase ◽  
No Synthase ◽  
Soluble Form ◽  
Control Group ◽  
Endothelial No Synthase ◽  
Basilar Arteries

✓ Endothelium-dependent vasodilation may be impaired during cerebral vasospasm following subarachnoid hemorrhage. Under normal circumstances nitric oxide (NO) released by endothelial cells induces relaxation of smooth muscle by activating the soluble form of guanylate cyclase within muscle cells. In this study the levels of both endothelial NO synthase, the enzyme that produces NO, and soluble guanylate cyclase were determined in canine basilar arteries in a double-hemorrhage model using Western blot immunoassays. Thirty dogs were assigned to three groups: Group D0, control; Group D2, dogs sacrificed 2 days after cisternal injection of blood; and Group D7, dogs given double cisternal injections of blood and sacrificed 7 days after the first injection. Constriction of the basilar artery was confirmed by arterial angiography. Portions of the affected arteries or the corresponding region in control animals were solubilized for sodium dodecylsulfate—polyacrylamide gel electrophoresis and Western blotting. A specific monoclonal antibody against endothelial NO synthase was used. The extract from basilar arteries showed two bands on the blots: 135 kD, characteristic of endothelial NO synthase, and 120 kD, which may be a degradation product of the enzyme. The densitometer values of the bands were presented as percentages of D0 control values. Although the total signal in the D7 group was less than that of the D0 control group (D2, 97% ± 22%; D7, 78% ± 40%), it was not statistically significant. The proportion of the 135-kD form decreased between Groups D0 and D7, but the difference was not significant. A single major band corresponding to the α-subunit of soluble guanylate cyclase was seen at 70 kD in the basilar artery extracts. The signals of D2 and D7 samples were 69%± 40% and 25% ± 18%, respectively. There was a significant difference between D7 and D0 (p < 0.001). The reduced expression of soluble guanylate cyclase may be related to the impairment of endothelium-dependent vasodilation in vasospasm.

scholarly journals Application of the 1-µsec pulsed-dye laser to the treatment of experimental cerebral vasospasm

1991 ◽  
Vol 75 (2) ◽  
pp. 271-276 ◽  
Author(s):  
Atsushi Teramura ◽  
Robert Macfarlane ◽  
Christopher J. Owen ◽  
Ralph de la Torre ◽  
Kenton W. Gregory ◽  
...  
Keyword(s):  
Cerebral Vasospasm ◽  
Basilar Artery ◽  
Laser Energy ◽  
Autologous Blood ◽  
Preliminary Investigation ◽  
Dye Laser ◽  
Pulsed Dye Laser ◽  
Content Type

✓ Laser energy of 480 nm was applied in 1-µsec pulses varying between 2.2 and 10 mJ to in vitro and in vivo models of cerebral vasospasm. First, the pulsed-dye laser was applied intravascularly via a 320-µm fiber to basilar artery segments from six dogs. The segments were mounted in a vessel-perfusion apparatus and constricted to, on average, 70% of resting diameter by superfusion with dog hemolysate. Immediate increase in basilar artery diameter occurred to a mean of 83% of control. In a second model, the basilar artery was exposed transclivally in the rabbit. In three normal animals, superfusion of the artery with rabbit hemolysate resulted in a reduction of mean vessel diameter to 81% of control. Following extravascular application of the laser, vessels returned to an average of 106% of the resting state. In six rabbits, the basilar artery was constricted by two intracisternal injections of autologous blood, 3 days apart. Two to 4 days after the second injection, the basilar artery was exposed. Extravascular laser treatment from a quartz fiber placed perpendicular to the vessel adventitia resulted in an immediate 53% average increase in caliber to an estimated 107% of control. No reconstriction was observed over a period of up to 5 hours. Morphologically, damage to the arterial wall was slight. This preliminary investigation suggests that the 1-µsec pulsed-dye laser may be of benefit in the treatment of cerebral vasospasm.

scholarly journals Alteration of Basilar Artery Rho-Kinase and Soluble Guanylyl Cyclase Protein Expression in a Rat Model of Cerebral Vasospasm following Subarachnoid Hemorrhage

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Chih-Jen Wang ◽  
Pei-Yu Lee ◽  
Bin-Nan Wu ◽  
Shu-Chuan Wu ◽  
Joon-Khim Loh ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Protein Kinase ◽  
Protein Expression ◽  
Cerebral Vasospasm ◽  
Basilar Artery ◽  
Guanylyl Cyclase ◽  
Autologous Blood ◽  
Rho Kinase ◽  
Soluble Guanylyl Cyclase ◽  
Western Blots

Background and Purpose. The vasoconstrictor endothelin-1 (ET-1) has been implicated in the pathogenesis of cerebral vasospasm following subarachnoid hemorrhage (SAH). Previous results showed that CGS 26303, an endothelin converting enzyme (ECE) inhibitor, effectively prevented and reversed arterial narrowing in animal models of SAH. In the present study, we assessed the effect of CGS 26303 on neurological deficits in SAH rats. The involvement of vasoactive pathways downstream of ET-1 signaling in SAH was also investigated.Methods. Sprague-Dawley rats were divided into five groups (n=6/group): (1) normal control, (2) SAH, (3) SAH+vehicle, (4) SAH+CGS 26303 (prevention), and (5) SAH+CGS 26303 (reversal). SAH was induced by injecting autologous blood into cisterna magna. CGS 26303 (10 mg/kg) was injected intravenously at 1 and 24 hr after the initiation of SAH in the prevention and reversal protocols, respectively. Behavioral changes were assessed at 48 hr after SAH. Protein expression was analyzed by Western blots.Results. Deficits in motor function were obvious in the SAH rats, and CGS 26303 significantly improved the rate of paraplegia. Expressions of rho-kinase-II and membrane-bound protein kinase C-δand rhoA were significantly increased, while those of soluble guanylyl cyclaseα1andβ1as well as protein kinase G were significantly decreased in the basilar artery of SAH rats. Treatment with CGS 26303 nearly normalized these effects.Conclusions. These results demonstrate that the rhoA/rho-kinase and sGC/cGMP/PKG pathways play pivotal roles in cerebral vasospasm after SAH. It also shows that ECE inhibition is an effective strategy for the treatment of this disease.

scholarly journals Acute stimulation of the soluble guanylate cyclase does not impact on left ventricular capacitance in normal and hypertrophied porcine hearts in vivo

2018 ◽  
Vol 315 (3) ◽  
pp. H669-H680 ◽  
Author(s):  
Alessio Alogna ◽  
Michael Schwarzl ◽  
Martin Manninger ◽  
Nazha Hamdani ◽  
Birgit Zirngast ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Soluble Guanylate Cyclase ◽  
Diastolic Pressure ◽  
Aortic Pressure ◽  
Left Ventricular ◽  
Concentric Hypertrophy ◽  
Ventricular Compliance ◽  
Left Ventricular Compliance ◽  
Stimulation Of

Experimental data indicate that stimulation of the nitric oxide-soluble guanylate cyclase(sGC)-cGMP-PKG pathway can increase left ventricular (LV) capacitance via phosphorylation of the myofilamental protein titin. We aimed to test whether acute pharmacological sGC stimulation with BAY 41-8543 would increase LV capacitance via titin phosphorylation in healthy and deoxycorticosteroneacetate (DOCA)-induced hypertensive pigs. Nine healthy Landrace pigs and 7 pigs with DOCA-induced hypertension and LV concentric hypertrophy were acutely instrumented to measure LV end-diastolic pressure-volume relationships (EDPVRs) at baseline and during intravenous infusion of BAY 41-8543 (1 and 3 μg·kg−1·min−1 for 30 min, respectively). Separately, in seven healthy and six DOCA pigs, transmural LV biopsies were harvested from the beating heart to measure titin phosphorylation during BAY 41-8543 infusion. LV EDPVRs before and during BAY 41-8543 infusion were superimposable in both healthy and DOCA-treated pigs, whereas mean aortic pressure decreased by 20–30 mmHg in both groups. Myocardial titin phosphorylation was unchanged in healthy pigs, but total and site-specific (Pro-Glu-Val-Lys and N2-Bus domains) titin phosphorylation was increased in DOCA-treated pigs. Bicoronary nitroglycerin infusion in healthy pigs ( n = 5) induced a rightward shift of the LV EDPVR, demonstrating the responsiveness of the pathway in this model. Acute systemic sGC stimulation with the sGC stimulator BAY 41-8543 did not recruit an LV preload reserve in both healthy and hypertrophied LV porcine myocardium, although it increased titin phosphorylation in the latter group. Thus, increased titin phosphorylation is not indicative of increased in vivo LV capacitance. NEW & NOTEWORTHY We demonstrate that acute pharmacological stimulation of soluble guanylate cyclase does not increase left ventricular compliance in normal and hypertrophied porcine hearts. Effects of long-term soluble guanylate cyclase stimulation with oral compounds in disease conditions associated with lowered myocardial cGMP levels, i.e., heart failure with preserved ejection fraction, remain to be investigated.

Abstract 1415: Activation of Soluble Guanylate Cyclase Regulates Phosphodiesterase 5A Localization and Restores Anti-adrenergic Action of Sildenafil despite Nitric Oxide Synthase Inhibition

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Takahiro Nagayama ◽  
Manling Zhang ◽  
Eiki Takimoto ◽  
David A Kass
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Soluble Guanylate Cyclase ◽  
Synergistic Effects ◽  
Adrenergic Stimulation ◽  
Adrenergic Activity ◽  
Oxide Synthase

Background: We have shown that inhibition of cyclic GMP-phosphodiesterase 5A (PDE5A) by sildenafil (SIL) blunts cardiomyocyte β-adrenergic stimulation, but this effect depends on the activity of endothelial nitric oxide synthase (eNOS) to generate a specific pool of cyclic GMP. PDE5A normally localizes at Z-bands in myocytes, but localization is more diffuse in cells with eNOS chronically inhibited. Here, we tested whether the influence of eNOS on PDE5A localization and anti-adrenergic action depends upon cyclic GMP. Methods and Results: Mouse in vivo hemodynamics were assessed by pressure-volume analysis. Isoproterenol (ISO: 20 ng/kg/min, iv ) stimulated contractility was inhibited by SIL (100 μg/kg/min, iv ), however this did not occur in mice given N w -nitro-L-arginine methyl ester (L-NAME: 1 mg/mL in drinking water for 1 week) to inhibit NOS. Myocytes transfected with an adenoviral vector encoding a fusion protein (PDE5A-DSred) in vivo were subsequently isolated and examined for PDE5A/α-actinin localization. Normal cells showed strong co-localization, whereas L-NAME-treated cells had diffuse PDE5A distribution. If L-NAME was stopped for 1-wk washout, SIL regained anti-adrenergic activity, and PDE5A z-band localization was restored. If L-NAME was continued but combined with Bay 41– 8543 (BAY: 30 mg/kg/day, po ), a soluble guanylate cyclase (sGC) activator, both PDE5A localization and SIL anti-adrenergic action were also restored. Chronic L-NAME suppressed phosphorylation of vasodilator-stimulated protein (VASP), a marker of protein kinase G (PKG) activity, in hearts acutely exposed to ISO+SIL. After L-NAME washout or L-NAME+BAY, VASP phosphorylation with ISO+SIL was restored. Conclusion: NOS-dependent modulation of both PDE5A sarcomere localization and anti-adrenergic activity depends upon sGC-derived cyclic GMP, and is linked to PKG activation. This suggests sGC activators may have synergistic effects with PDE5A inhibitors.

α2-Adrenergic-mediated tubular NO production inhibits thick ascending limb chloride absorption

2001 ◽  
Vol 281 (4) ◽  
pp. F679-F686 ◽  
Author(s):  
Craig F. Plato ◽  
Jeffrey L. Garvin
Keyword(s):  
Guanylate Cyclase ◽  
Soluble Guanylate Cyclase ◽  
Chloride Transport ◽  
Receptor Activation ◽  
Inhibitory Effect ◽  
No Production ◽  
Thick Ascending Limb ◽  
Chloride Absorption ◽  
Ly 83583

Stimulation of α2-adrenergic receptors inhibits transport in various nephron segments, and the thick ascending limb of the loop of Henle (THAL) expresses α2-receptors. We hypothesized that selective α2-receptor activation decreases NaCl absorption by cortical THALs through activation of NOS and increased production of NO. We found that the α2-receptor agonist clonidine (10 nM) decreased chloride flux ( J Cl) from 119.5 ± 15.9 to 67.4 ± 13.8 pmol · mm−1 · min−1 (43% reduction; P < 0.02), whereas removal of clonidine from the bath increased J Cl by 20%. When NOS activity was inhibited by pretreatment with 5 mM N G-nitro-l-arginine methyl ester, the inhibitory effects of clonidine on THAL J Clwere prevented (81.7 ± 10.8 vs. 71.6 ± 6.9 pmol · mm−1 · min−1). Similarly, when the NOS substrate l-arginine was deleted from the bath, addition of clonidine did not decrease THAL J Cl from control (106.9 ± 11.6 vs. 132.2 ± 21.3 pmol · mm−1 · min−1). When we blocked the α2-receptors with rauwolscine (1 μM), we found that the inhibitory effect of 10 nM clonidine on THAL J Cl was abolished, verifying that α2, rather than I1, receptors mediate the effects of clonidine in the THAL. We investigated the mechanism of NOS activation and found that intracellular calcium concentration did not increase in response to clonidine, whereas pretreatment with 150 nM wortmannin abolished the clonidine-mediated inhibition of THAL J Cl, indicating activation of phosphatidylinositol 3-kinase and the Akt pathway. We found that pretreatment of THALs with 10 μM LY-83583, an inhibitor of soluble guanylate cyclase, blocked clonidine-mediated inhibition of THAL J Cl. In conclusion, α2-receptor stimulation decreases THAL J Cl by increasing NO release and stimulating guanylate cyclase. These data suggest that α2-receptors act as physiological regulators of THAL NO synthesis, thus inhibiting chloride transport and participating in the natriuretic and diuretic effects of clonidine in vivo.

Synthesis and vectorial export of cGMP in airway epithelium: expression of soluble and CNP-specific guanylate cyclases

1993 ◽  
Vol 265 (6) ◽  
pp. L598-L605 ◽  
Author(s):  
C. A. Geary ◽  
M. F. Goy ◽  
R. C. Boucher
Keyword(s):  
Natriuretic Peptide ◽  
Guanylate Cyclase ◽  
Cyclic Nucleotide ◽  
Soluble Guanylate Cyclase ◽  
Basolateral Membrane ◽  
Primary Cultures ◽  
Respiratory Epithelium ◽  
Maximal Velocity ◽  
Lower Efficiency ◽  
Cyclic Monophosphate

Guanosine 5'-cyclic monophosphate (cGMP) is an important modulator of fluid balance in many epithelia. We examined its metabolism in primary cultures of human airway epithelia. Sodium nitroprusside increased cGMP levels 30-fold, suggesting that the respiratory epithelium expresses a soluble guanylate cyclase; however, endogenous nitric oxide production was not detected. cGMP levels could also be increased by C-type natriuretic peptide (CNP), but not by atrial natriuretic peptide, brain natriuretic peptide, or Escherichia coli heat-stable enterotoxin, indicating expression of a CNP-specific membrane-bound guanylate cyclase. The one-half effective concentration for CNP was 40 nM and the maximal velocity was 56.7 pmol cGMP.mg protein-1.h-1. After CNP stimulation, approximately 60% of the total synthesized cGMP was preferentially exported from the polarized epithelial cells across the basolateral membrane by a probenecid-sensitive process. Isoproterenol-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) export revealed a similar export pattern and probenecid sensitivity, although a lower efficiency of export (27% of total cAMP was exported). Consistent with previous reports, export of neither cyclic nucleotide was saturable at the concentrations tested. We conclude that the respiratory epithelium expresses a soluble guanylate cyclase, a CNP-specific receptor, and a novel vectorial cyclic nucleotide export mechanism.

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