Thyrotropin-releasing hormone and gonadotropin-releasing hormone-associated peptide modulation of [Ca2+]i in human lactotrophs.
The effect of thyrotropin-releasing hormone (TRH) and gonadotropin-releasing hormone-associated peptide (GAP) was studied on both secretion and intracellular free Ca2+ concentrations ([Ca2+]i) in human pituitary cells cultured from prolactin (PRL)-secreting tumors. Secretion was measured during a 30-min incubation period and we used a microspectrofluorimetric method in individual cells and indo-1 as the fluorescent probe. TRH (10(-8) M) significantly increased PRL release in five out of the six cell populations. In these five cases, more than 68% of individual cells responded to TRH by an increase in [Ca2+]i. No significant increase in PRL secretion was found in another culture in which TRH increased [Ca2+]i in only 37% of the cells. The effect of GAP (10(-7) M) was studied in five cell populations. In three of them, a decrease of 20% to 51% of the PRL basal secretory rate was observed under GAP. GAP inhibited [Ca2+]i in respectively 59%, 46% and 94% of the cells from these cultures. The inhibitory effect of GAP was blocked by a pertussis toxin (PT) pretreatment which demonstrates the involvement of a PT-sensitive G-protein in GAP action. In two other cultures, GAP did not significantly alter PRL secretion or individual cell [Ca2+]i. These observations suggest that GAP might play a role in the control of PRL secretion in the human.
Dufy-Barbe
L
L
Laboratoire de Neurophysiologie, CNRS URA 1200, Université de Bordeaux II, France.
Bresson
L
L
Vacher
P
P
Odessa
M F
MF
San Galli
F
F
Rivel
J
J
Guérin
J
J
D000236:Adenoma / Q000378:metabolism / Q000473:pathology; D000293:Adolescent; D000328:Adult; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000378:metabolism; D037342:Pertussis Toxin; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000378:metabolism* / Q000473:pathology; D011388:Prolactin / Q000378:metabolism*; D015175:Prolactinoma / Q000378:metabolism* / Q000473:pathology; D011498:Protein Precursors / Q000494:pharmacology*; D015290:Second Messenger Systems; D012636:Secretory Rate / Q000187:drug effects; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D009363:Neoplasm Proteins; D011498:Protein Precursors; D010566:Virulence Factors, Bordetella; C050502:gonadotropin releasing hormone associated peptide; D007987:Gonadotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium