The interactive effects of VIP, PHI, GHRH, and SRIF on the release of growth hormone from cultured adenohypophysial cells in cattle.
The effects of hypothalamic peptides [vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), growth hormone (GH)-releasing hormone (GHRH) and somatostatin (SRIF) on GH release from cultured bovine adenohypophysial cells were studied. The cells were incubated for 2 h with the peptides after preincubation for 3.5 days. At doses from 10(-9) to 10(-7)M VIP, the amount of GH released was significantly greater than in the controls (P < 0.05 to P < 0.001). PHI (10(-10 to 10(-7)M did not alter the bovine GH concentration in the media. Incubation with the media containing 10(-7)M GHRH, 10(-7)M VIP, and combined treatment with the VIP plus GHRH increased GH by 186, 40 and 182%, respectively (P < 0.001). Furthermore, although VIP-induced GH release was significantly decreased by SRIF compared with the treatment with VIP alone (P<0.001), the VIP significantly blunted the inhibitory effect of the SRIF on GH release by 24% when compared with that of the SRIF plus GHRH without the VIP (P < 0.05). GH release in combined treatments with VIP, GHRH and SRIF was significantly less than that of the VIP plus GHRH (P < 0.001), but it was significant 29% increase compared with the SRIF plus GHRH (P < 0.05). The combined effects of the VIP (10(-7)M) with GHRH (10(-7), 10(-8) and 10(-10)M significantly induced GH release compared with the controls (P < 0.001), but no additive effect was not observed when compared with the GHRH alone. The results indicate that VIP, but not PHI, acts directly on cultured adenohypophysial cells to induce GH release in cattle.
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Laboratory of Animal Reproduction, Faculty of Agriculture, Iwate University, Morioka, Japan.
Hashizume
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Ohashi
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Kanematsu
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D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D013006:Growth Hormone / Q000187:drug effects / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006727:Hormone Antagonists / Q000494:pharmacology*; D010451:Peptide PHI / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011863:Radioimmunoassay; D013004:Somatostatin / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D006727:Hormone Antagonists; D010451:Peptide PHI; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone