Cyclic adenosine monophosphate is not part of the transduction chain by which cell-swelling induces secretion in either normal or tumor-derived GH4C1 pituitary cells.
We have evaluated whether cyclic adenosine monophosphate (cAMP) generation plays a role in the burst of hormone secretion caused by osmotic cell-swelling in tumor-derived and normal pituitary cells. Up to 45% hyposmolarity induced a dose-dependent increase in prolactin (PRL) secretion, but had no effect on cAMP generation. However, hyposmolarity inhibited forskolin-induced cAMP accumulation in a dose-dependent manner, but had no effect on 3-isobutyl-1-methyl-xanthine (IBMX)-induced cAMP accumulation. Ca2+ depletion of the medium partially blocked the inhibitory effect of hyposmolarity on forskolin-induced cAMP generation and completely blocked stimulation of PRL secretion by hyposmolarity. High levels of K+ in medium inhibited forskolin-induced cAMP generation, while thyrotropin-releasing hormone (TRH) enhanced it. Our results indicate that in both GH4C1 and normal pituitary cells, cAMP is not a regulatory factor for hormone secretion induced by cell-swelling.
Wang
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Department of Medicine, Oregon Health Sciences University, Portland 97201.
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D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D048429:Cell Size; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D007038:Hypotonic Solutions; D008297:Male; D009994:Osmolar Concentration; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism* / Q000473:pathology; D011188:Potassium / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D007038:Hypotonic Solutions; D005576:Colforsin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D000242:Cyclic AMP; D011188:Potassium; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine