Effects of angiographic contrast medium on isolated canine coronary arteries

Sexual-dimorphism in human immune system aging

Differences in immune function and responses contribute to health- and life-span disparities between sexes. However, the role of sex in immune system aging is not well understood. Here, we characterize peripheral blood mononuclear cells from 172 healthy adults 22-93 years of age using ATAC-seq, RNA-seq, and flow cytometry. These data reveal a shared epigenomic signature of aging including declining naïve T cell and increasing monocyte and cytotoxic cell functions. These changes are greater in magnitude in men and accompanied by a male-specific decline in B-cell specific loci. Age-related epigenomic changes first spike around late-thirties with similar timing and magnitude between sexes, whereas the second spike is earlier and stronger in men. Unexpectedly, genomic differences between sexes increase after age 65, with men having higher innate and pro-inflammatory activity and lower adaptive activity. Impact of age and sex on immune phenotypes can be visualized at https://immune-aging.jax.org to provide insights into future studies.

Effects of Dimeric Radiographic Contrast Medium Iotrolan on Swine Renal Arteries

RATIONALE AND OBJECTIVES

To investigate whether the lower incidence of vasodilatation upon vascular injection of iotrolan, as compared with monomeric contrast media, is solely the result of its isotonicity.

MATERIALS AND METHODS

In an organ bath, isolated segments of swine renal arteries, uncontracted or precontracted by 10 microm phenylephrine, were incubated with increasing concentrations of iotrolan-300, iohexol-300, iomeprol-300, iomeprol-150, and mannitol solutions with the same molarity as the contrast media.

RESULTS

At equal iodine and equimolar concentrations, iotrolan-300 relaxed precontracted arteries less than iohexol-300, iomeprol-300, and iomeprol-150, which was, like iotrolan-300, iso-osmolar to blood (P < 0.05). There was no significant difference between iohexol-300 and iomeprol-300 (P > 0.05). Iotrolan had no significant effect on the basal tonus of the vessels whereas iohexol and iomeprol induced a slight relaxation.

CONCLUSIONS

Iotrolan, even at equimolar concentrations, resulted in less vasorelaxation than iohexol and iomeprol. Both osmolarity and chemotoxicity contribute to the greater vasorelaxant effect on swine renal artery of monomeric contrast media when compared to that of the nonionic dimeric contrast medium, iotrolan.

Nonionic contrast media iohexol and iomeprol decrease renal arterial tone: comparative studies on human and porcine isolated vascular segments

RATIONALE AND OBJECTIVES

The vasoconstriction of the renal arteries is frequently considered as a crucial factor for radiocontrast-induced nephropathy. A direct effect of iodinated radiographic contrast medium (RCM) on vascular smooth muscle is supposed to be one component of the vascular response. We studied the effect of the nonionic RCM iomeprol and iohexol on the tonus of isolated human and porcine renal arteries in vitro.

METHODS

In an organ bath renal arterial rings, uncontracted or precontracted by 10 micromol/L phenylephrine were incubated with increasing concentrations (15-103 mg iodine/mL) of iohexol, iomeprol, and mannitol solution isoosmolar to the contrast media. In a part of the preparations the endothelium was destroyed. Human vessels were obtained from tumor nephrectomy specimens of 10 patients.

RESULTS

In human experiments iomeprol and iohexol (P < 0.05) relaxed renal arterial rings whereas mannitol produced concentration-dependent contractions. The relaxation by both contrast media was slightly attenuated upon increasing their concentration. The differences between mannitol solutions and RCM were statistically significant (P < 0.001) at concentrations of 57 mg iodine/mL and higher. Precontracted rings were significantly stronger relaxed by the RCM compared with mannitol (P < 0.001). The contrast medium induced relaxation did not depend on the presence of an intact endothelium (P > 0.05). Experiments with renal arterial segments prepared from swine showed similar results, with stronger relaxations than the human preparations.

CONCLUSION

Iomeprol and iohexol relaxed isolated renal arterial segments. These observations are in contradiction with the hypothesis that contrast media induce nephropathy by a direct vasoconstrictive effect on vascular smooth muscle. They do not exclude, however, a reduction of renal blood flow by other factors like liberation of hormones.

Iodinated radiographic contrast media inhibit the capacitative calcium entry into smooth muscle cells of the swine renal artery

RATIONALE AND OBJECTIVES

To investigate whether nonionic, iodinated, radiographic contrast media (RCM) could modulate calcium release from or calcium entry into smooth muscle cells of the swine renal artery.

METHODS

Intracellular calcium concentrations of isolated myocytes loaded with the calcium-sensitive dye fluo-3 were analyzed using a fluorescence imaging system. Calcium signals were compared with isometric contractions of vascular segments in an organ bath. The effects of the triiodinated monomer iomeprol were compared with those of a mannitol solution.

RESULTS

Stimulation of alpha-receptors by phenylephrine caused a biphasic calcium signal. Transient liberation of calcium from intracellular stores triggered the sustained entry of extracellular calcium (capacitative entry). Iomeprol and mannitol slightly inhibited the initial transient spike to the same extent. The calcium influx was reversibly inhibited by RCM by about 50%. Up to a concentration of 40 mmol/L, the inhibition induced by iomeprol was significantly higher than that induced by mannitol (P < 0.05-0.01). In isolated arterial segments, relaxation of the contraction phase depending on the calcium influx was significantly higher with the RCM than with mannitol (P < 0.01).

CONCLUSIONS

Vasodilatation by CM is associated with a reduction in the capacitative entry of calcium. The mechanism of this effect is not clear, but it can be ruled out that it is mainly due to the high osmolarity of these compounds.

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.

Variable effects of iodinated contrast media on different rabbit arteries in vitro

Vasoconstriction caused by iodinated contrast media (CM) has been considered specific for the renal artery only. We examined the vascular effect of CM in rabbit carotid, aorta, renal, iliac, mesenteric and celiac arteries and found that other arteries also respond with a contraction to CM. Isolated arterial rings were exposed to diatrizoate (high osmolar CM), iohexol (low osmolar CM) or glucose solution, and the isometric contraction response was expressed as percentage of an initial KCl control contraction. Diatrizoate evoked contractions of 82% (carotid), 63% (aorta), 30% (renal), 24% (iliac), 28% (mesenteric) and 18% (celiac), respectively. Iohexol caused contractions of 31% (carotid), 24% (aorta), 15% (renal) and 14% (iliac), whereas the mesenteric and celiac arteries were relaxed by iohexol. A high osmolar glucose solution elicited contractions of 78%, 77%, 11%, 27%, 3% and 5%, respectively, in the arteries. CM have contraction potency in arterial vasculature other than the renal artery.

Role of intracellular calcium stores in contrast medium-induced renal vasoconstriction

RATIONALE AND OBJECTIVES

Renovascular smooth muscle contractility, an important factor in contrast media-induced nephrotoxicity, depends on intracellular Ca2+ concentration, which is composed of extracellular Ca2+ influx and intracellular Ca2+ release. These factors were investigated in contrast media-induced renal vasoconstriction in an in vitro model.

METHODS

KCl-induced isometric contractions of rabbit renal artery were compared with contractions elicited by contrast media (diatrizoate, iohexol, iopamidol). Measurements were made after incubation with the Ca2+ channel blockers nifedipine, verapamil, and diltiazem to assess the role of extracellular Ca2+ influx and after ryanodine and thapsigargin to investigate the role of intracellular Ca2+ release.

RESULTS

The Ca2+ channel blockers partially inhibited contractions induced by contrast media, while KCl-induced contractions were completely abolished. Ryanodine and thapsigargin also markedly inhibited contrast media-induced contractions.

CONCLUSION

Ionic and nonionic contrast media induced quantitatively different renal vasocontractions. Ca2+ channel blockers inhibited this vasocontraction only slightly compared with intracellular Ca2+ release blockers.

Ionic mechanisms contributing to the vasorelaxant properties of iodinated contrast media: a comparison of iohexol and iodixanol in the rabbit isolated aorta

1. We have used rings of rabbit thoracic aorta to investigate the vasorelaxant properties of two different classes of non-ionic iodinated radiographic contrast media (IRCM) and the mechanisms, underlying their mode of action. Iohexol (a triiodinated monomer) was compared with iodixanol (a hexaiodinated dimer). 2. Iohexol and iodixanol both relaxed phenylephrine (0.3 microM) constricted rabbit aorta in a concentration-dependent manner that did not depend on the presence of an intact endothelium. When expressed as a function of iodine concentration, iodixanol caused significantly less relaxation than iohexol. However, the extent of relaxation was similar for both IRCM when expressed on a molar basis. Furthermore, increasing the molarity of the buffer to comparable levels with mannitol evoked only a small (approximately 15%) relaxation of phenylephrine-induced tone. 3. Ouabain (10 microM) significantly inhibited both iohexol- and iodixanol-induced relaxations by approximately 30%. 5-(N-Ethyl-N-isopropyl)-amiloride (EIPA, 100 nM) significantly inhibited iohexol-induced relaxation to the same extent as ouabain, but did not alter the vasorelaxant effect of iodixanol. Co-incubation with ouabain and EIPA had an additive effect in the case of iohexol, increasing inhibition of relaxation to approximately 60%, whereas inhibition of iodixanol-induced relaxation by the combination of ouabain plus EIPA did not differ from that of ouabain alone. 4. Replacing NaCl with N-methyl-D-glucamine (NMDG) to lower extracellular [Na+] and thereby inhibit Na(+)-Ca2+ exchange, attenuated the relaxation evoked by iohexol or by iodixanol (by approximately 25%) in each case. 5. We conclude that iohexol- and iodixanol-induced vasorelaxation in rabbit aorta is mediated through a direct action on vascular smooth muscle that is not simply a consequence of altered osmolality. It involves modulation of the Na(+)-K+ ATPase and, in the case of iohexol, Na(+)-H+ exchange. Both agents also appear to modulate Na(+)-Ca2+ exchange, through direct and/or indirect mechanisms. This is the first study to show specific pharmacological differences between monomeric and dimeric contrast media in vascular smooth muscle.

Ca2+ and cyclic adenosine monophosphate involvement in radiographic contrast medium-induced renal vasoconstriction

PURPOSE

To investigate the role of extracellular Ca2+ and cyclic 3'-5' adenosine monophosphate (cAMP), a known second messenger promoting smooth muscle relaxation, in preventing renal vasoconstriction induced by radiographic contrast medium (RCM).

MATERIALS AND METHODS

Isometric contractions of rabbit renal artery were elicited by potassium chloride and increasing concentrations of meglumine/sodium diatrizoate. To determine the contribution of extracellular Ca2+, nifedipine, a blocker of voltage-dependent L-type Ca2+ channels (VDCC), was applied. The contribution of cAMP was investigated by applying the nonspecific phosphodiesterase (PDE) inhibitors papaverine and theophylline and the specific PDE inhibitor milrinone, all of which prevent degradation of cAMP. Forskolin, an activator of cAMP by stimulating adenylyl cyclase (AC), was also investigated.

RESULTS

RCM elicited contractions that were 24.5% of the KCl control contraction, which was reduced by nifedipine (100 mumol/L) by 34.7%. Papaverine, theophylline, and milrinone inhibited RCM-induced contractions by 69.8%, 64.3%, and 43.7%, respectively. Forskolin reduced the response by 82.2%.

CONCLUSION

Ca2+ influx through VDCC partially contributes to RCM-induced renal artery vasoconstriction. Intracellular cAMP appears to be an important second messenger pathway for prevention of this response. These findings emphasize the role of second messenger systems involved in adverse RCM effects and the potential prevention of these effects.

Vasodilatative and vasoconstrictive effects of angiography contrast media

During angiography contrast media (CM) induces changes in vessel tone. The pathophysiological reasons for this are poorly understood. In this short review the anatomical structures and physiological factors involved in vessel tone are described, and previous and recent findings in vitro and in vivo concerning the effect of CM on vessel tone are discussed. Although multifactorial, the main effect seems to result from a direct action of the CM on the vessel wall. For a particular CM formulation, the effect is due to a combination of its osmolality, molecular properties as well as electrolyte content. In vitro experiments performed in iso-osmolar solutions of pure CM suggest the CM interfere with the cellular mechanisms controlling intracellular calcium. When injected intravascularly, CM may cause either vasodilatation and vasoconstriction. Vasodilatation is the most frequent effect when CM is injected into a vessel while vasoconstriction is relatively uncommon. Both vasodilatation and vasoconstriction can be caused by all types of CM.

Measurement of regional cerebral blood flow in the dog using ultrafast computed tomography. Experimental validation

The applicability, feasibility, reproducibility, and accuracy of the method of measuring regional cerebral blood flow using ultrafast computed tomography were evaluated in 25 dogs under varying physiological and pathophysiological conditions. Regional cerebral blood flow values were 75.6 +/- 29.4 ml/100 g/min (mean +/- standard deviation) for the hemisphere, 68.4 +/- 28.2 ml/100 g/min for the basal ganglia, 41.2 +/- 15.0 ml/100 g/min for the internal capsule, and 80.8 +/- 37.2 ml/100 g/min for the neocortex. Measurements made 10 minutes apart were significantly (p less than 0.05) correlated. Simultaneous measurements of regional cerebral blood flow by the microsphere and ultrafast computed tomography methods showed a significant (p less than 0.05) correlation for the hemisphere (r = 0.95), basal ganglia (r = 0.95), and neocortex (r = 0.94) but not for the internal capsule (r = 0.51). Microsphere and ultrafast computed tomography regional cerebral blood flow values were also in agreement in radiation-damaged brain with appreciable blood-brain barrier breakdown, and the two methods demonstrated similar responsiveness of regional cerebral blood flow to alterations in arterial carbon dioxide tension. The accuracy and sensitivity of the ultrafast computed tomography technique suggests that it affords a useful new tool for studying normal and abnormal regional cerebral blood flow.

Effects of ionic and nonionic contrast media on coronary diameter and blood flow in chronically instrumented dogs

The effects of intracoronary administration of ionic and nonionic contrast media on coronary circulation were studied in 14 chronically instrumented dogs. A pair of 10 MHz piezoelectric crystals and an electromagnetic flow probe were placed on the left circumflex coronary artery, under sterile conditions, to measure the epicardial coronary diameter and coronary blood flow, respectively. A polyethylene tube for drug infusion was inserted into the circumflex coronary artery proximal to the sonomicrometers. In the conscious dogs (n = 8), iopamidol, 2 ml and 5 ml increased the coronary diameter by 64 +/- 19 microns and 66 +/- 19 microns and coronary blood flow by 35 +/- 10% and 61 +/- 18%, respectively (p less than 0.01 vs control level). Meglumine diatrizoate, 2 ml and 5 ml, increased coronary diameter by 102 +/- 20 microns and 114 +/- 18 microns and coronary blood flow by 87 +/- 32% and 107 +/- 26%, respectively (p less than 0.01 vs control level). In the anesthetized dogs (n = 6), a bolus intracoronary injection of 5 ml iopamidol and meglumine diatrizoate within few seconds increased the coronary diameter by 103 +/- 23 microns and 164 +/- 39 microns (p less than 0.05) and increased the coronary blood flow by 126 +/- 33% and 180 +/- 40% (p less than 0.05), respectively. Balloon denudation of the endothelium was performed in six anesthetized dogs. The increases in coronary diameter and coronary blood flow after a bolus injection of contrast medium remained the same after the denudation. Thus application of iopamidol seems to be more suitable than meglumine diatrizoate for quantitative coronary angiography because of the milder and more transient effects on coronary circulation.

Left ventriculography induced coronary artery spasm

Angiographic contrast material is generally considered a vasodilator, although in vitro experiments have documented a spasmogenic effect. In this report we describe a patient with exercise and rest angina who developed spasm of the right coronary artery immediately following left ventricular angiography. The patient was treated successfully with calcium channel blockers. This is the first reported case of left ventricular angiography-induced coronary artery spasm.

The effect of substituted sydnonimines on coronary smooth muscle relaxation and cyclic guanosine monophosphate levels

In vitro experiments on precontracted canine coronary arteries were performed to study the direct relaxant effects of molsidomine (MOLS) and its active metabolite, SIN-1, and to determine if there is a relationship between effect and cGMP level elevations. The effects of MOLS and SIN-1 were compared with those of a classic vasodilator, nitroglycerin (NTG). At equimolar doses (10(-6)M) SIN-1 exerted greater relaxant effect than NTG (80 +/- 2% and 60 +/- 5%, respectively) in spite of the fact that it produced less of an increase in cyclic guanosine monophosphate (cGMP) levels. cGMP levels fell rapidly after they peaked, but relaxation was maintained. cGMP elevation preceded the induction of relaxation by NTG but not that induced by SIN-1. Relaxation occurred faster after NTG than after SIN-1. Since SIN-1 has a greater relaxant effect than NTG in spite of the fact that SIN-1 induces less of an increase in cGMP levels and the fact that the peak elevation does not precede the onset of relaxation, the causal nexus between GMP level elevation and relaxation effect after sydnonimines should be challenged.