Brain uptake and anticancer activities of vincristine and vinblastine are restricted by their low cerebrovascular permeability and binding to plasma constituents in rat

• Published in: Cancer chemotherapy and pharmacology 1990-01, Vol.26 (4), p.263-268
• Main Authors: GREIG, N. H, SONCRANT, T. T, SHETTY, H. U, MOMMA, S, SMITH, Q. R, RAPOPORT, S. I
• Format: Article
• Language: English
• Subjects: Animals; Antineoplastic agents; Biological and medical sciences; Blood Proteins - metabolism; Blood-Brain Barrier - drug effects; Brain - blood supply; Brain - metabolism; Brain Neoplasms - drug therapy; Brain Neoplasms - metabolism; Brain Neoplasms - pathology; Brain Neoplasms - secondary; Capillary Permeability - drug effects; Carcinoma 256, Walker - drug therapy; Carcinoma 256, Walker - metabolism; Carcinoma 256, Walker - pathology; Cerebrovascular Circulation - drug effects; Chemotherapy; Male; Mathematics; Medical sciences; Neoplasm Transplantation; Perfusion; Pharmacology. Drug treatments; Rats; Rats, Inbred Strains; Vinblastine - pharmacokinetics; Vinblastine - pharmacology; Vincristine - pharmacokinetics; Vincristine - pharmacology
• ISSN: 0344-5704; 1432-0843
• DOI: 10.1007/BF02897227

Unidirectional blood-brain barrier transfer of the lipophilic anticancer agents vincristine and vinblastine was studied in anesthetized rats, using an isolated, in situ brain perfusion technique. Drug binding to plasma constituents was also measured. Despite the high lipophilicity of these agents (the log octanol/physiological saline partition coefficient equalled 2.14 and 1.68, respectively), the cerebrovascular permeability-surface area product, PA, of vincristine in plasma was only 0.49 x 10(-4) ml s-1 g-1 for parietal cerebral cortex, whereas that of vinblastine was too low for determination. These values are similar to those of water-soluble, poorly diffusible nonelectrolytes. The PAs were significantly higher in the absence of plasma protein, being 1.24 x 10(-4) and 5.36 x 10(-4) ml s-1 g-1, respectively. Even these values, determined by brain perfusion of protein-free buffer, were lower than would be expected from the lipophilicity of the agents. The results suggest that additional factors, such as steric hindrance and molecular charge distribution, related to the chemical and geometric structure and the large size of vincristine and vinblastine (molecular weight, 825 and 814 daltons, respectively) restrict their passage across the blood-brain barrier. As a consequence of their paradoxically low permeability at the blood-brain barrier and restrictive binding to plasma and blood constituents, doses of both agents that cause significant inhibition of extracerebral Walker 256 carcinosarcoma tumor implants in rat have no effect on tumor located in the brain.