Pflügers Archiv

, Volume 418, Issue 6, pp 531–537

Measurements of intracellular calcium and contractility in human ciliary muscle

  • F. Stahl
  • A. Lepple-Wienhues
  • M. Kuppinger
  • U. Schneider
  • M. Wiederholt
Transport Processes, Metabolism and Endocrinology, Kidney, Gastrointestinal Tract and Exocrine Glands

DOI: 10.1007/BF00370567

Cite this article as:
Stahl, F., Lepple-Wienhues, A., Kuppinger, M. et al. Pflügers Arch (1991) 418: 531. doi:10.1007/BF00370567

Abstract

Electromechanical and pharmacomechanical coupling was investigated in human ciliary muscle by measuring the intracellular free calcium in single cultured ciliary muscle cells and the contractility in meridional ciliary muscle strips. The basal resting calcium concentration was 75±8.7 nmol/l, n=23. Application of acetylcholine (0.1 mmol/l) and carbachol (0.1 mmol/l) resulted in an initial [Ca2+]i peak followed by a recovery phase and a [Ca2+]i plateau. The initial [Ca2+]i peak was still observed in the absence of extracellular calcium and in the presence of verapamil (0.1 mmol/l). During its plateau [Ca2+]i was decreased by withdrawal of extracellular calcium or application of verapamil (0.1 mmol/l). Depolarization induced by a high level of extracellular potassium yielded only a small transient [Ca2+]i peak without a [Ca2+]i plateau. In isolated ciliary muscle strips, muscarinic stimulation (carbachol 0.1 mmol/l) resulted in an initial phasic and a subsequent tonic contraction. Removal of external calcium reduced the phasic contraction to 30.6±4.4% (n=8) and completely abolished the tonic one. Verapamil (0.1 mmol/l) had only a slight relaxing effect when applied during the tonic contraction. We conclude that human ciliary muscle contraction is mediated by calcium release from intracellular stores and calcium entry through calcium channels, which are most probably receptor-operated. Depolarization of the muscle cell membrane and calcium entry through voltage-operated calcium channels do not contribute significantly to human ciliary muscle contraction.

Key words

Ciliary muscleCell cultureIntracellular calciumIsolated ciliary muscle stripsContractilityAcetylcholineCarbachol

Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • F. Stahl
    • 1
  • A. Lepple-Wienhues
    • 1
  • M. Kuppinger
    • 1
  • U. Schneider
    • 1
  • M. Wiederholt
    • 1
  1. 1.Institut für Klinische PhysiologieKlinikum Steglitz der Freien Universität BerlinBerlin 45Federal Republic of Germany