PMID- 8194104
OWN - NLM
STAT- MEDLINE
DCOM- 19940629
LR  - 20190920
IS  - 0143-4160 (Print)
IS  - 0143-4160 (Linking)
VI  - 15
IP  - 3
DP  - 1994 Mar
TI  - GHRP-6 induces a biphasic calcium response in rat pituitary somatotrophs.
PG  - 247-58
AB  - The mechanism of action of His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6), a synthetic 
      peptide which specifically induces the secretion of growth hormone (GH) in rat 
      somatotrophs, is still poorly understood. We have studied the effects of GHRP-6 
      on the cytosolic free calcium concentration ([Ca2+]i) of somatotrophs in primary 
      culture. [Ca2+]i was monitored in individual somatotrophs by dual emission 
      microspectrofluorimetry, using Indo-1 as the intracellular fluorescent Ca2+ 
      probe. A short application of GHRP-6 (10(-5) M, 10 s) induced a biphasic Ca2+ 
      response in most cells (44%), which consisted in a rapid and large rise in 
      [Ca2+]i followed by sustained oscillations. This response is dose dependent in a 
      range of concentrations from 10(-10) to 10(-5) M. The first phase of the GHRP-6 
      response persisted in the absence of Ca2+ in the extracellular medium, whereas 
      the second phase was inhibited. The application of Ca2+ channel blockers like 
      cadmium chloride (200 microM) or PN-200-110 (200 nM) also prevented the second 
      phase. Conversely, when the cells were pretreated with thapsigargin (TG) (100 
      nM), the first phase of the GHRP-6 Ca2+ response was abolished, whereas the 
      second phase alone was preserved. When the cells were depleted in PKC by 
      incubation with 10(-6) M PMA for 24 h, the second phase of the GHRP-6 response 
      was inhibited, and only the first phase was maintained. These results were 
      corroborated by using phloretin, a PKC inhibitor. These data show that GHRP-6 
      induces a biphasic elevation of the [Ca2+]i in rat somatotrophs. The first phase 
      is probably due to mobilization of the intracellular Ca2+ stores, whereas the 
      second phase is a PKC-dependent process.
FAU - Bresson-Bepoldin, L
AU  - Bresson-Bepoldin L
AD  - Laboratoire de Neurophysiologie, CNRS URA 1200, Universite de Bordeaux II, 
      France.
FAU - Dufy-Barbe, L
AU  - Dufy-Barbe L
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Netherlands
TA  - Cell Calcium
JT  - Cell calcium
JID - 8006226
RN  - 0 (Oligopeptides)
RN  - 4H7N4I6X6A (growth hormone releasing hexapeptide)
RN  - EC 2.7.11.13 (Protein Kinase C)
RN  - NI40JAQ945 (Tetradecanoylphorbol Acetate)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Amino Acid Sequence
MH  - Animals
MH  - Calcium/*metabolism
MH  - Cells, Cultured
MH  - Female
MH  - Fluorescent Antibody Technique
MH  - Molecular Sequence Data
MH  - Oligopeptides/*pharmacology
MH  - Pituitary Gland, Anterior/cytology/*metabolism
MH  - Protein Kinase C/metabolism
MH  - Rats
MH  - Rats, Wistar
MH  - Tetradecanoylphorbol Acetate/pharmacology
EDAT- 1994/03/01 00:00
MHDA- 1994/03/01 00:01
CRDT- 1994/03/01 00:00
PHST- 1994/03/01 00:00 [pubmed]
PHST- 1994/03/01 00:01 [medline]
PHST- 1994/03/01 00:00 [entrez]
AID - 0143-4160(94)90064-7 [pii]
AID - 10.1016/0143-4160(94)90064-7 [doi]
PST - ppublish
SO  - Cell Calcium. 1994 Mar;15(3):247-58. doi: 10.1016/0143-4160(94)90064-7.