Dual effects of manganese on prolactin secretion |
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Authors: | J E Merritt B L Brown |
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Affiliation: | Department of Human Metabolism & Clinical Biochemistry, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX, UK. |
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Abstract: | The effect of Mn2+ (a commonly used Ca2+ antagonist) on prolactin secretion from pituitary cells was investigated. In the presence of normal extracellular Ca2+ levels (2.5mM), Mn2+ inhibited basal, TRH- and K+- stimulated prolactin secretion. The Ca2+ ionophore, A23187, partially overcame the inhibitory effect of Mn2+. However, in the presence of low extracellular Ca2+ (less than 100 microM), which decreased basal prolactin secretion and abolished any stimulatory effects of TRH or K+, a paradoxical stimulatory effect was observed with Mn2+ in the presence of A23187. In the presence of Ca2+, Mn2+ appeared to be inhibitory due to its Ca2+ antagonistic effects, but at low Ca2+ levels, intracellular stimulatory effects of Mn2+ became apparent. |
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Keywords: | Reprint requests to: J.E. Merritt |
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