Carbachol-induced [Ca2+]i oscillations in single smooth muscle cells of guinea-pig ileum

J Physiol. 1996 Apr 15;492 ( Pt 2)(Pt 2):315-28. doi: 10.1113/jphysiol.1996.sp021311.

Abstract

1. Changes in cytosolic Ca2+ concentration ([Ca2+]i) produced by carbachol (CCh) were measured in single smooth muscle cells of guinea-pig ileum using a Ca(2+)-sensitive fluorescent dye, fura-2, to clarify the underlying mechanisms of muscarinic [Ca2+]i oscillations. 2. Half of the cells, when exposed to 0.2 microM CCh, exhibited repeated changes in [Ca2+]i giving a serrated appearance. The oscillatory changes in [Ca2+]i were very similar to those evoked by increasing extracellular K(+) concentration ([K+]o) to 30 mM, which were abolished by removal of extracellular Ca2+, nifedipine and La3+, but remained unchanged after depletion of internal Ca2+ stores with cyclopiazonic acid, thapsigargin and ryanodine. 3. Every individual [Ca2+]i oscillation was just like a [Ca2+]i increase generated spontaneously in about 8% of cells or triggered by an action potential evoked by a current pulse in current-clamped cells. 4. In the remaining half of the cells exposed to 0.2 microM CCh, slower [Ca2+]i oscillations were elicited and every individual [Ca2+]i oscillation was always preceded by the fast brief increase in [Ca2+]i. 5. [Ca2+]i oscillations elicited by 2 microM CCh were temporally and functionally distinct from those induced by high [K+]o. They were more or less regular in the periodicity and pattern, comprised pacemaker potential-like [Ca2+]i increases or sinusoidal types of [Ca2+]i increases, and could be elicited even in 100 mM K+(o). 6. Removal of extracellular Ca2+ or application of nifedipine, methoxyverapamil (D600), diltiazem or La3+ during CCh (2 micro M)-induced [Ca2+]i oscillations caused them to disappear. In cells i which internal Ca2+ stores were depleted, 2 microM CCh did not evoke [Ca2+]i oscillations but occasionally induced single or repeated generation of the increase in [Ca2+]i with a serrated appearance. 7. The results indicate that CCh can induce two types of [Ca2+]i oscillation in guinea-pig ileal smooth muscle cells; one arises from Ca2+ influx associated with action potential discharges and the other from periodic release of Ca2+ from internal stores. The latter [Ca2+]i oscillation requires extracellular Ca2+ to sustain it.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium / physiology
  • Calcium Channel Blockers / pharmacology
  • Carbachol / pharmacology*
  • Cytosol / metabolism*
  • Electrophysiology
  • Extracellular Space / metabolism
  • Guinea Pigs
  • Ileum / cytology
  • Ileum / metabolism*
  • Ileum / physiology
  • Male
  • Muscarinic Agonists / pharmacology*
  • Muscle, Smooth / cytology
  • Muscle, Smooth / metabolism*
  • Muscle, Smooth / physiology
  • Oscillometry
  • Osmolar Concentration
  • Potassium / metabolism

Substances

  • Calcium Channel Blockers
  • Muscarinic Agonists
  • Carbachol
  • Potassium
  • Calcium