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Sources of Ca

Arnaldo Fim Neto1, Rosana A Bassani2, Pedro X de Oliveira2

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Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
|September 16, 2018
PubMed
Summary

Insect hearts use calcium from both external influx and internal stores for contraction, similar to vertebrates. Heart rate also influences contraction and relaxation dynamics.

Keywords:
Ca2+Inotropic activityInsect heartL-type Ca2+ channelsSarcoplasmic reticulumStimulation rate

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Area of Science:

  • Cardiology
  • Insect Physiology
  • Calcium Signaling

Background:

  • Insect and vertebrate hearts generate rhythmic electrical activity for fluid propulsion.
  • Limited information exists on inotropic activity generation in insect hearts.
  • Understanding calcium sources is crucial for insect cardiac function studies.

Purpose of the Study:

  • Investigate the sources of calcium (Ca2+) for contraction in Tenebrio molitor hearts.
  • Assess the impact of heart rate on cardiac function.
  • Determine the roles of L-type calcium channels and sarcoplasmic reticulum in insect cardiac contraction.

Main Methods:

  • Experiments conducted on Tenebrio molitor hearts perfused in situ.
  • Electrical pacing at near-physiological rates to control heart rate.
  • Manipulated extracellular Ca2+ concentration and used pharmacological agents (D600, caffeine, thapsigargin, KB-R7943) to study calcium pathways.

Main Results:

  • Increasing heart rate depressed contraction amplitude and accelerated relaxation.
  • Elevated extracellular Ca2+ enhanced contraction amplitude, sensitive to L-type Ca2+ channel blockade.
  • Caffeine and thapsigargin impaired Ca2+ accumulation by the sarcoplasmic reticulum, reducing contraction.
  • L-type Ca2+ channel blockade further depressed contraction in thapsigargin-treated hearts.

Conclusions:

  • In Tenebrio molitor hearts, inotropic and lusitropic activities are modulated by heart rate.
  • Calcium for contraction relies on both influx via L-type channels and release from the sarcoplasmic reticulum.
  • Insect cardiac calcium handling mechanisms share similarities with vertebrates.