Profound inhibition of myogenic tone in rat cardiac allografts is due to eNOS- and iNOS-based nitric oxide and an intrinsic defect in vascular smooth muscle contraction.

BACKGROUND: The physiological consequences of inducible NO synthase (iNOS) expression were studied in allograft coronary arteries by pressure myography. METHODS AND RESULTS: Septal coronary arteries (diameter, 200.6+/-3.3 microm) were harvested from allograft and isograft hearts, and their myogenic properties were measured before and after iNOS and nonselective NOS inhibition with aminoguanidine (AG, 100 micromol/L) and N(G)-nitro-L-arginine methyl ester (L-NAME) (200 micromol/L). Fura 2 fluorescence microscopy was used to measure [Ca(2+)](i) in isolated endothelial cells. Monoclonal anti-iNOS immunostains demonstrated iNOS protein in day 2, 7, 14, and 28 allograft vessels, but only in day 2 isograft vessels. Myogenic tone was profoundly inhibited in allograft vessels from day 4 onward. In day 4 allograft vessels, these differences were abolished by L-NAME but not AG, suggesting greater basal release of eNOS-based NO from allograft endothelium. Fluorescence measurements confirmed elevation of [Ca(2+)](i) in day 4 allograft endothelium, providing a mechanism for enhanced eNOS activity. For days 7 to 28, AG potentiated myogenic tone in allograft but not isograft vessels, indicating that vasoactive iNOS-based NO was present. In mature vessels, constriction via agonist- and depolarization-mediated mechanisms showed parallel inhibition, suggesting an intrinsic defect in vascular smooth muscle cell contraction. CONCLUSIONS: Our data indicate that the profound inhibition of myogenic tone in allograft arteries involves direct vasodilation by eNOS- and iNOS-based NO, as well as an intrinsic defect in vascular smooth muscle contraction. The hemodynamic profile resulting from these changes in allograft resistance vessel function would favor movement of extracellular fluid from the intravascular space into the myocardial interstitium, resulting in edema, increased ventricular stiffness, and poor ventricular performance.

Esophagocolic anastomotic stricture repaired twelve years after original interposition.

Successful resection of a long, tight, unyielding cervical esophagocolic anastomosis with mobilization of the colon interposition transplant through a sternal splitting incision 12 years after the primary surgery is reported. The colon transplant with its vascular bundle was dissected with less difficulty than expected and 5 cm of increased length was obtained to make a new neck anastomosis without tension.

Endothelial and myogenic regulation of coronary artery tone in the mouse.

Ventricular septal (150-200 microm) arteries were isolated from the hearts of six-week-old CD-1 mice and mounted on a pressure myograph. Equilibration of the vessels at 70 mm Hg for 60 min resulted in the development of spontaneous myogenic tone. Maximum tone observed in these vessels greatly exceeded that previously reported in septal arteries from rats. Inhibition of endothelin ET(A) and endothelin ET(B) receptors with bosentan (1 and 10 microM) reduced basal tone. Endothelin release required intact endothelial cells. The alpha(1)-adrenceptor selective agonists phenylephrine and methoxamine did not cause change in coronary tone, while the alpha(2)-adrenceptor selective agonists 6-allyl-2-amino5,6,7, 8-tetrahydro-4H-thiazolo-[4,5-d]azepin-dihydrochloride (BHT 920) and clonidine produced vasodilatation. Noradrenaline (1 nM-10 microM) induced a concentration-dependent vasodilatation, which was inhibited by concurrent treatment with yohimbine (10 microM) and propranolol (20 microM). Vasodilatation due to BHT 920 was abolished with vessel denudation, indicating the endothelial location of alpha(2)-adrenoceptors. Acetylcholine (1 nM-10 microM) caused an endothelium dependent vasodilatation; inhibition of nitric oxide synthase with N(omega)-nitro-L-arginine methyl ester attenuated this response. The endothelium-dependent vasodilators bradykinin and substance P produced no vasomotor effect in mouse coronary arteries. Differences between human and murine responses may impact on the relevance of the mouse coronary artery for use as a potential model of human coronary vessel diseases.