Microtubule—macrotubule transformations induced by volatile anesthetics. Mechanism of macrotubule assembly

• Published in: Journal of ultrastructure research Vol. 57; no. 3; pp. 237 - 250
• Main Author: Hinkley, Robert E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.01.1976
• Subjects: Animals; Astacoidea; Axons - ultrastructure; Enflurane - pharmacology; Ethers - pharmacology; Halothane - pharmacology; Isoflurane - pharmacology; Methoxyflurane - pharmacology; Microtubules - drug effects; Microtubules - ultrastructure; Staining and Labeling; Trichloroethylene - pharmacology
• ISSN: 0022-5320; 1878-2345
• DOI: 10.1016/S0022-5320(76)80113-X

Halothane, a widely used volatile anesthetic, transforms crayfish axonal microtubules measuring 240 Å in diameter into enlarged tubular structures (macrotubules) averaging 460 Å in diameter. Tannic acid and negative staining techniques have been used to compare the substructure of microtubules and macrotubules and to determine the mechanism of macrotubule assembly. The tubular transformation is initiated by the dissociation of microtubules into component protofilaments which reassemble into unique “twisted ribbon” intermediate structures. Twisted ribbons appear to form macrotubules when adjacent ribbon gyres come into register and join. Macrotubule formation is rapid and at least partially reversible. Methoxyflurane, isoflurane, enflurane, and trichloroethylene also produce macrotubules by a series of structural modifications identical to those described for halothane. Fluroxene and ether dissociate microtubules but do not lead to macrotubule formation. These data provide new information concerning the effects of volatile anesthetics on microtubular structure and the structural polymorphism of microtubule protein.