Lithium-induced decrease in spontaneous Ca2+ oscillations in single GH3 rat pituitary cells.

Abstract

1. Measurement of [Ca2+]i in single rat pituitary GH3 cells by dynamic single cell imaging techniques demonstrated that under basal conditions there is a large variation in the temporal pattern of [Ca2+]i signalling between individual cells ranging from high frequency asynchronous oscillations to quiescence. 2. We have reported previously that treatment of GH3 cells with 1 mM Li+ (a concentration used therapeutically in the treatment of manic depression) for 7 days reduces basal and thyrotrophin-releasing hormone (TRH)-stimulated levels of mass inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. In the present study, we show that this is associated with a reduction in the number of cells exhibiting basal Ca2+ oscillations over a sampling period of 60 s, whereas the maximum amplitude of oscillations is unaffected. 3. The pattern of [Ca2+]i responses to the agonist TRH varied considerably between individual cells, making quantitation of the responses difficult; however, data obtained from measurements made on a population of cells showed that increases in peak [Ca2+]i induced by high concentrations of TRH were reduced in cells treated with 1 mM Li+ for 7 days relative to control cells. 4. The sensitivity of the phosphoinositide pathway to [Ca2+]i was investigated by loading GH3 cells with BAPTA/AM at a concentration sufficient to lower 'basal' [Ca2+]i in a population of cells and to inhibit agonist-stimulated increases in [Ca2+]i. Under these conditions, basal and TRH-stimulated mass Ins(1,4,5)P3 levels were unaffected. 5. These results demonstrate that a 7-day Li+ treatment leads to an alteration in Ca2+ signalling, in particular by reducing the number of cells exhibiting high frequency Ca2+ oscillations under basal conditions. The significance of these results to the clinical effectiveness of Li+ in the treatment of manic depression is discussed.

• Authors: M A Varney, A Galione, S P Watson
• Journal: British journal of pharmacology (Br J Pharmacol) Vol. 112 Issue 2 Pg. 390-5 (Jun 1994) ISSN: 0007-1188 [Print] England
• PMID: 8075856 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Egtazic Acid
• Thyrotropin-Releasing Hormone
• Inositol 1,4,5-Trisphosphate
• Prolactin
• Lithium
• 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
• Calcium

Topics

• Animals
• Calcium (metabolism)
• Cell Line
• Egtazic Acid (analogs & derivatives, pharmacology)
• Image Processing, Computer-Assisted
• Inositol 1,4,5-Trisphosphate (metabolism)
• Lithium (pharmacology)
• Pituitary Gland (cytology, drug effects, metabolism)
• Prolactin (metabolism)
• Rats
• Thyrotropin-Releasing Hormone (pharmacology)