The radiosensitizer nicotinamide inhibits arterial vasoconstriction
| Autor: | Gordon D. Kennovin, F W Flitney, D. G. Hirst |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Male
Niacinamide Radiation-Sensitizing Agents Vascular smooth muscle Blood Pressure Pharmacology Muscle Smooth Vascular chemistry.chemical_compound medicine Animals Radiology Nuclear Medicine and imaging Rats Wistar Phenylephrine Dose-Response Relationship Drug Nicotinamide business.industry General Medicine Anatomy Rats Perfusion B vitamins medicine.anatomical_structure chemistry Mechanism of action Vasoconstriction medicine.symptom business medicine.drug Artery |
| Zdroj: | The British Journal of Radiology. 67:795-799 |
| ISSN: | 1748-880X 0007-1285 |
| DOI: | 10.1259/0007-1285-67-800-795 |
| Popis: | Nicotinamide (NA) is currently entering clinical trials as a radiosensitizer. A major component of its activity is the improvement of tumour oxygenation resulting from a reduction in microregional ischaemia. NA is known to reduce arterial blood pressure in rodents, suggesting a vascular component in its mechanism of action. We have used an ex vivo system to study the direct action of NA on the contractile properties of vascular smooth muscle. Isolated pieces of rat tail artery were internally perfused with Krebs' solution at a constant flow rate so that constriction of the arterial smooth muscle could be measured as an increase in perfusion pressure. Transient vasoconstrictor responses lasting up to 10 min were induced with bolus injections (10 microliters) of phenylephrine, at concentrations ranging from 10(-5) to 10(-2) M, into the internal perfusate whereas a constant increase in vasoconstrictor tone, giving perfusion pressures of 43-84 mmHg, was induced by constantly perfusing with PE (5 x 10(-6) M) or raising the K+ concentration of the Krebs' solution to 122 mM. The addition of NA to the perfusate significantly reduced the size of the transient vasoconstrictor responses in a dose-dependent manner and induced the precontracted vessels to relax. This action of NA could not be blocked either by N omega-nitro-L-arginine methyl ester (L-NAME), indomethacin or propranolol. We conclude that direct effects on supplying blood vessels probably contribute to the oxygenating action of NA in tumours, though the precise mechanism remains obscure. |
| Databáze: | OpenAIRE |
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