Influence of oligopeptide aldehydes on intracellular Ca2+ concentration in rat pituitary cells

Gyula Horváth, Angéla Gyévai, György Rappay, Gábor B. Makara, Iván Nagy

Research output: Contribution to journalArticle

Abstract

We investigated the effects of some synthetic tripeptide aldehydes, earlier shown to influence pituitary hormone secretion and 45Ca2+ uptake, on the intracellular free Ca2+ concentration ([Ca2+]i) of rat anterior pituitary cells in suspension. Boc-D-Phen- Leu-Phenylalaninal or Boc-D-Phe-Leu-Prolinal in the tested range of 1-100 or 200 μM, respectively, were ineffective in influencing basal [Ca2+]i but caused a concentration-dependent inhibition in K+ (25 mM)-induced [Ca2+]i elevation. The IC50 of both effects was about 50 μM. In contrast, they did not interfere with the stimulation caused by the calcium channel agonist BAY K 8644 and were also ineffective in influencing the receptor-mediated stimulus of thyrotropin-releasing hormone on [Ca2+]i. On the basis of the present and foregoing results the possible involvement of calcium channels is discussed, but different mechanisms mediating the tripeptide aldehyde inhibition are also considered. A third tripeptide aldehyde. Boc-Gln-Leu-Lysinal (Boc-GLL), showed ionophore-like properties. This nontoxic substance caused a dose-dependent rise up to 400% (at 100 μM) in [Ca2+]i. Its effect is not mediated by voltage-dependent calcium channels, as it cannot be inhibited either by the classicalp calcium channel antagonists verapamil and nifedipine, or by the above-mentioned inhibitory tripeptide aldehydes. When we decreased the extracellular Ca2+ concentration by the addition of 4 mM EGTA, the effect was inverted and Boc-GLL caused a large fall in [Ca2+]i. We suggest that Boc-GLL may open cell membrane pores through which Ca2+ moves along the concentration gradient. The calcium flux can be inhibited by 20 mM Mg2+ and 100 μM Co2+ but not by 500 μM La3+. Thus, tripeptide aldehydes. depending on their structure, may decrease or increase [Ca2+]i via uncoventional mechanisms and may serve as tools for dissecting details of cell calcium homeostasis.

Original languageEnglish
Pages (from-to)305-312
Number of pages8
JournalEuropean Journal of Pharmacology: Molecular Pharmacology
Volume225
Issue number4
DOIs
Publication statusPublished - Apr 10 1992

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Keywords

  • Ca channels
  • Ca ionophore
  • Co
  • Fura-2
  • Intracellular Ca
  • La

ASJC Scopus subject areas

  • Pharmacology

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