An adenosine derivative cooperates with TSH and Graves' IgG to induce Ca 2+ mobilization in single human thyroid cells

Abstract

Digital video imaging indicated that about 80% of fura-2-loaded single human thyroid cells responded to TSH, resulting in an increase in intracellular Ca 2+ concentration ([Ca 2+] i). Most of the TSH-sensitive cells further responded to N 6-( l-2-phenylisopropyl)-adenosine (PIA) showing a transient [Ca 2+] i rise in a PIA dose-dependent manner. Addition of PIA prior to TSH administration had no effect or showed only a slight [Ca 2+] i increase, but in about 80% of the cells, regardless of the response to PIA, the addition of TSH after PIA resulted in a higher transient [Ca 2+] i response than that in the absence of PIA. Inactivation of G i G 0 by pertussis toxin (PTX) treatment markedly reduced the effect of PIA on TSH action to the level induced by PIA alone. Immunoglobulin fractions obtained from two Graves' patients with high TSAb (antibody activity measured by cAMP response) activity induced [Ca 2+] i increase and cooperated with PIA. Under the same conditions, TSH-dependent cAMP accumulation was inhibited by PIA. These results suggest that adenosine A 1 receptor is expressed in human thyroid cells in primary culture as well as in FRTL-5 rat thyroid cells, and that in the presence of adenosine, TSH or Graves' IgG signal tends to be directed to the Ca 2+ pathway in the human thyroid.