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  • Title: Calcium antagonistic effects of an angiographic contrast medium in vitro. A comparison of the effects of iohexol with the effects of nifedipine in isolated arteries.
    Author: Karstoft J, Bååth L, Jansen I, Edvinsson L.
    Journal: Invest Radiol; 1995 Jan; 30(1):21-7. PubMed ID: 7759212.
    Abstract:
    RATIONALE AND OBJECTIVES: Vasodilatation is a well-known side effect of contrast media. Contrast media inhibit the action of vasoconstrictors. The nonionic contrast medium, iohexol, inhibits vasoactive substances to a lesser extent than ionic contrast media. Iohexol inhibited the action of vasoconstrictors in a way that raised suspicion of a calcium antagonistic effect of the medium. The authors test this hypothesis by comparing the inhibitory effect of iohexol with the inhibitory effect of a calcium antagonist (nifedipine). The vasoconstrictors were KCl, which depends on potential-operated calcium channels, and histamine, endothelin-1, and prostaglandin F2 alpha (PGF2 alpha), which depend on receptor-operated calcium channels. METHODS: Segments of rabbit coronary arteries were mounted between two L-shaped prongs in tissue baths containing calcium-free buffer, calcium-free buffer with 10(-8) M nifedipine, or iohexol. One of the vasoconstrictors, KCl, histamine, endothelin-1, or PGF2 alpha, was added to induce a level of activation. Thereafter, increasing concentrations of CaCl2 were added in a stepwise manner, and the contractile responses of the vessel segments were recorded. RESULTS: Addition of CaCl2 caused concentration-dependent vasoconstrictions in the buffer. The effect of adding CaCl2 was inhibited in the buffer with nifedipine and in iohexol when the vessels were activated with histamine, endothelin-1, or PGF2 alpha. When the vessels were activated with the potential-operated calcium channel-dependent vasoconstrictor, KCl, the effect of adding CaCl2 was inhibited in the buffer with nifedipine but not in iohexol. CONCLUSIONS: In vitro, iohexol had the same effect as the calcium antagonist nifedipine on the action of receptor-operated calcium channel-dependent vasoconstrictors. This suggests a calcium antagonistic effect of iohexol on the action of the ROC.
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