Altered responsiveness to hypophysiotrophic hormones of perifused rat pituitary tumours.
Since growth hormone (GH) and prolactin (Prl) secretion by human pituitary tumours is often influenced by the hypophysiotrophic hormones thyrotrophin-releasing hormone (TRH) and somatostatin (SRIF), we have examined the responses of several transplantable rat pituitary tumours to these substances in a perifusion apparatus. The MStT/W15 tumour did not alter its secretion of GH and Prl in response to TRH, SRIF, or a partially purified porcine hypothalamic extract containing GH-releasing activity; normal rat pituitaries show clear responses to each of these substances. Theophylline and dibutyryl cyclic AMP each provoked increased GH and Prl release from the tumour. A second specimen of the MStT/W15 tumour and a specimen of the MStT/W5 tumour behaved in a manner identical to the original MStT/W15, showing no response to TRH or SRIF, but releasing both GH and Prl when theophylline or dibutyryl cyclic AMP was given. The MtT/F4 tumour increased its secretion of GH in response to TRH, 10 mug/ml, and theophylline, but no effect was seen with lower concentrations of TRH or with SRIF; Prl secretion by the F4 tumour was increased by theophylline, but TRH and SRIF had no effect. The autonomy demonstrated in these experimental tumours may be due to a loss of specific hypophysiotrophic hormone receptors or of secretory activating mechanisms.
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D004357:Drug Synergism; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D007031:Hypothalamus; D009374:Neoplasms, Experimental / Q000378:metabolism; D010477:Perfusion; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface; D013004:Somatostatin / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D011956:Receptors, Cell Surface; D013004:Somatostatin; D013973:Thyrotropin-Releasing Hormone; D003994:Bucladesine; D011388:Prolactin; D013006:Growth Hormone; D013806:Theophylline