Growth hormone inhibits growth hormone secretion from the rainbow trout pituitary in vitro.
Growth hormone (GH) secretion in salmonids and other fish is under the control of a number of hypothalamic factors, but negative feed-back regulation by circulating hormones can also be of importance for the regulation of GH secretion. Mammalian studies show that GH has a negative feed-back effect on its own secretion. In order to elucidate if GH levels present a direct ultra-short negative feedback loop at the pituitary level GH secretion was studied in intact pituitaries from 50 g fish in an in vitro perifusion system. Following an initial equilibrium period pituitaries were exposed to five increasing concentrations (1-1,000 ng ml(-1)) of ovine GH (oGH) in 20-min steps, before being returned to a GH-free perifusion. Ovine GH caused a significant dose-dependent inhibition of GH secretion and it is concluded that GH can exert a direct negative feedback control on GH secretion at the pituitary level.
Agústsson
T
T
Department of Zoology, Göteborg University , Sweden. t.agustsson@zool.gu.se
Björnsson
B T
BT
D000818:Animals; D005246:Feedback / Q000502:physiology; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D066298:In Vitro Techniques; D017686:Oncorhynchus mykiss; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism
D013006:Growth Hormone