Effects of VIP and GRF on the release of growth hormone in perifused bovine adenohypophysis

Effect of Growth Hormone (GH)-Releasing Peptide (GHRP) on the Release of GH from Cultured Anterior Pituitary Cells in Cattle.

“…The potency of the GHRH-stimulated GH releasing effect over GHRP in the present study coincided with reports of previous studies on rat pituitary incubates [8], or in the perfusion of dispersed anterior pituitary cells in male rats [20]. Moreover, the bovine GH releasing effects could be seen at doses as low as 10-11 M GHRH in perfused adenohypophysis as reported by Hashizume and Kanematsu [22], or at doses as low as 10-12 M GHRH from bovine pituitary cells [29]. The bovine GH releasing effects of combined treatment with GHRP and GHRH were more effective than that with GHRP alone.…”

The Interactive Effects of VIP, PHI, GHRH and SRIF on the Release of Growth Hormone from Cultured Adenohypophysial Cells in Cattle.

“…As regards the higher potency in GHRH-stimulated bovine GH release than that obtained with VIP, the present study coincided with reports of previous studies on superfused rat pituitary reaggregated cells [12], and on perifused bovine anterior pituitary tissues [15]. It has been reported that the GH releasing effects of GHRH were maintained longer than that of VIP, suggesting that the somatotrophs might be stimulated to release GH for hours by a short period of GHRH action [15].…”

“…It has been reported that the GH releasing effects of GHRH were maintained longer than that of VIP, suggesting that the somatotrophs might be stimulated to release GH for hours by a short period of GHRH action [15]. It is also known that the half-life of VIP, as determined in the circulation, is approximately 3 min [2].…”

“…Earlier studies have demonstrated that VIP (10_6-10-8 M) stimulated GH release from perifused anterior pituitary tissues in cows [14,15] and goats [9]. In the present study we have shown that VIP is able to induce the release of GH by acting directly on the cultured adenohypophysial cells in steers, and that the VIP-stimulated bovine GH release could be seen at doses as low as 10-9 M. As far as we know, a direct action of VIP on GH release from cultured adenohypophysial cells has not yet been reported in cattle.…”

“…Rivier et al failed to observe GH releasing activity of VIP, PHI or glucagon on rat pituitary cells [13]. In cows, earlier studies demonstrated that VIP exerts a direct action on perifused adenohypophysial tissues to induce GH release, and that the effect of VIP is less potent than that of GHRH [14,15] Bovine GH concentrations in media were measured by a validated RIA method previously described by Johke [17]. The GH standard preparation and hormone for iodination were USDA bGH-Bl [19,20].…”