Involvement of mitochondria in intracellular calcium sequestration by rat gonadotropes

Cell Calcium. 1996 Dec;20(6):515-24. doi: 10.1016/s0143-4160(96)90094-9.

Abstract

Intracellular Ca2+ ([Ca2+]i) dynamics were studied in identified rat gonadotropes using the whole-cell patch-clamp technique in conjunction with Indo-1 photometry. The kinetics of depolarization-induced [Ca2+]i transients vary with Ca2+ load. In addition to a rapid initial decay, large (> 500 nM) [Ca2+]i transients have a slow plateau phase. Application of the mitochondrial inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP) significantly slows the decay of [Ca2+]i transients, consistent with stopping uptake of Ca2+ by mitochondria. CCCP causes a small increase of [Ca2+]i at rest. After a large Ca2+ entry the amount is much larger, consistent with release from a mitochondrial Ca2+ pool that fills during cytoplasmic Ca2+ loading. The rate of Ca2+ uptake by mitochondria is dependent upon [Ca2+]i. Consistent with previous studies, gonadotropin releasing hormone (GnRH) induces [Ca2+]i oscillations. The mitochondrial inhibitors CCCP and cyanide (CN-) terminate these oscillations. The mitochondrial ATP-synthase inhibitor oligomycin reduces the frequency and increases the amplitude of the oscillations. In the presence of ruthenium red (a non-specific blocker of the mitochondrial Ca(2+)-uniporter) in the pipette, GnRH does not induce rhythmic [Ca2+]i oscillations. We suggest that mitochondria play a significant role in the rapid clearance of cytosolic Ca2+ loads in gonadotropes and participate in GnRH-induced periodic [Ca2+]i oscillations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium-Transporting ATPases / metabolism
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology
  • Cells, Cultured / drug effects
  • Cells, Cultured / enzymology
  • Cells, Cultured / ultrastructure
  • Endoplasmic Reticulum / enzymology
  • Gonadotropin-Releasing Hormone / pharmacology
  • Kinetics
  • Male
  • Membrane Potentials / physiology
  • Mitochondria / drug effects
  • Mitochondria / metabolism*
  • Orchiectomy
  • Patch-Clamp Techniques
  • Pituitary Gland / cytology*
  • Rats
  • Rats, Sprague-Dawley
  • Uncoupling Agents / pharmacology

Substances

  • Uncoupling Agents
  • Gonadotropin-Releasing Hormone
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone
  • Calcium-Transporting ATPases
  • Calcium