Inhibition of growth hormone release by prostaglandins in immature domestic fowl (Gallus domesticus).

The effect of prostaglandin (PG) E1, PGE2 and PGF2 alpha on GH secretion has been assessed in immature domestic fowl. The intravenous or subcutaneous administration of PGE1 and PGE2 (at a dose of approximately 200 microgram/kg) to 2-, 6- and 8-week-old cockerels consistently lowered plasma GH concentrations. This inhibition in GH secretion was observed for at least 40 min after administration of PGE1 and PGE2. The same dose of PGF2 alpha suppressed plasma GH levels in 2- and 6- week-old birds but the magnitude and duration of this response was less than that induced by PGE1 and PGE2. At this dose, administration of PGE1 and PGE2 resulted in overt signs of distress (e.g. gaping, panting, eye closure and postural instability) within 5-10 min of injection and the birds appeared to be sedated thereafter. Prostaglandin F2 alpha and lower doses of PGE1 and PGE2 did not have any apparent effect on behavior. These results suggest that prostaglandins inhibit GH secretion in birds although this may reflect a non-specific stress response.