Effects of Ghrelin on Growth Hormone Secretion from Cultured Adenohypophysial Cells in Cattle

Abstract

To clarify the direct effects of ghrelin on growth hormone (GH) release from anterior pituitary (AP) cells in cattle, GH-releasing effects of human ghrelin (hGhrelin) and rat ghrelin (rGhrelin) on bovine AP cells were compared with those of GH-releasing hormone (GHRH) in vitro. The AP cells were obtained from Holstein steers and were incubated for 2 h with the peptides after incubating in DMEM for 3 days. hGhrelin and rGhrelin significantly stimulated GH release from the cultured cells at doses from 10(-10) to 10(-7) M and from 10(-9) to 10(-7) M, respectively (P<0.05). The rates of increase in GH at 10(-10), 10(-9), 10(-8) and 10(-7) M hGhrelin were 26, 26, 59 and 100% compared with controls, respectively, and those of increase in GH at 10(-9), 10(-8) and 10(-7) M rGhrelin were 58, 74 and 106%, respectively. GHRH significantly increased GH concentrations in cultured media at a dose as low as 10(-13) M compared with the control (P<0.05). When hGhrelin (10(-8) M) and GHRH (10(-8) M) were added together, the release of GH induced by both peptides was significantly greater than that by hGhrelin alone (P<0.05), and tended to be greater than that by GHRH alone. Somatostatin (SS, 10(-7) M) significantly blunted GH release induced by hGhrelin (10(-8) M) and GHRH (10(-8) M) (P<0.05). In the presence of SS, the percent increase in GH released with hGhrelin plus GHRH was 42% and 14% greater than that by either hGhrelin or GHRH alone, respectively (P<0.05). These results show that ghrelin directly stimulates the release of GH from anterior pituitary cells, and that SS modifies ghrelin-stimulated GH release in cattle.

Effects of retinoic acid on growth hormone-releasing hormone receptor, growth hormone secretagogue receptor gene expression and growth hormone secretion in rat anterior pituitary cells

“…In a perfusion system, GHRH and ghrelin stimulated GH release from isolated rat anterior pituitary cells in a dose-dependent manner at doses from 10 -10 to 10 -8 M [20]. Hashizume et al found that these peptides directly stimulate GH release from static cultured bovine anterior pituitary cells [21]. The present study used a static incubation system.…”

In vitro and in vivo effects of ghrelin on luteinizing hormone and growth hormone release in goldfish

“…In a preliminary study, we found that human ghrelin also stimulates GH release from dispersed pituitary cells in vitro (unpublished observations), adding more support for our present findings. Ghrelin stimulates GH release from the dispersed pituitary cells of rats (23,38), pigs (11), and cattle (12). Stimulatory effects of ghrelin on GH release were also reported from studies using the incubated whole pituitaries of tilapia (20,39), eel (19), and trout (18).…”

Gastric estrogen directly induces ghrelin expression and production in the rat stomach

“…It is known that ghrelin stimulates GH release from anterior pituitary cells (Kojima et al 1999, Yamazaki et al 2002, Hashizume et al 2003, Malagon et al 2003, and several recent studies have indicated that this effect is mediated via not only the direct, but also the indirect pathways, including the vagal afferent nerve (Date et al 2002, Sakata et al 2003. In addition to GH release, ghrelin also stimulates food intake and adiposity in humans and rodents (Tschop et al 2000, Wren et al 2000, Asakawa et al 2001, Shintani et al 2001, indicating that these physiological effects of ghrelin play an important role in growth regulation and energy homeostasis.…”