Effects of growth hormone (GH)-releasing hormone and its analogs on GH secretion from cultured adenohypophysial cells in cattle.
The effects of the human growth hormone (GH)-releasing hormone (hGRF(1-44)-NH2: hGRF-44), bovine GRF (bGRF(1-44)-NH2: bGRF-44), and their analogs (hGRF(1-29)-NH2, [D-Ala2]- hGRF(1-29)-NH2, bGRF(1-29)-NH2,[D-Ala2,Ala15]-bGRF(1-29)-NH2) as well as rat GRF(rGRF) on bovine GH release from anterior pituitary (AP) cells were studied in vitro in steers. The AP cells were incubated for 2 hr with the GRFs after preincubation for 3.5 d. Both of the hGRF-44 and hGRF(1-29)-NH2 (hGRF-29) significantly stimulated GH release from cultured cells at doses from 10(-14) to 10(-8)M (P < 0.01). The analog [D-Ala2]-hGRF-29 significantly induced GH release in media at doses from 10(-18) to 10(-8) M (P < 0.01). The bGRF-44, bGRF(1-29)-NH2 (bGRF-29), and [D-Ala2, Ala15]-bGRF-29 significantly induced GH release in media at doses as low as 10(-18), 10(-17), and 10(-16)M, respectively (P < 0.01). At doses from 10(-11) to 10(-8)M, there were no significant differences in GH-releasing potency between the hGRFs and bGRFs. The rGRF significantly stimulated GH release at doses ranging from 10(-14) to 10(-8) M (P < 0.01). The linear regression tests showed that the hGRFs, bGRFs, and rGRF, at doses from 10(-14) to 10(-8)M, induced GH release in a dose-related manner (P < 0.01). These results suggest that the hGRF, bGRF, and their analogs, as well as rGRF, are potent secretagogues of GH release from adenohypophysial cells in vitro in cattle.
Soliman
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Laboratory of Animal Breeding and 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 / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000031:analogs & derivatives / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D016014:Linear Models; D008297:Male; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats
D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone