Somatostatin: Its Influence on Plasma Levels of Growth Hormone, Prolactin and Thyrotropin in Sheep

Abstract

The influence of synthetic somatostatin (somatotropin-release-inhibiting factor, SRIF) on ovine growth hormone (oGH), prolactin (oPRL) and thyrotropin (oTSH) secretion was studied in eight immature ewe lambs (26 to 36 kg). In the first experiment, SRIF treatment was combined with an arginine infusion. The second study was conducted to examine the effect of SRIF on basal levels of oGH, oPRL and oTSH. The third study involved treatment with SRIF + thyrotropin-releasing hormone (TRH) as compared to TRH alone. The infusion of arginine resulted in a significant (P < .05) increase in plasma levels of oGH. SRIF treatment significantly (P <.05) decreased the oGH response to arginine. The oPRL response to arginine was present, but not significant because of wide between animal variability. SRIF treatment had no significant influence on plasma oTSH, or the oPRL response to arginine. The continuous infusion of SRIF for 1 hr had no significant (P < .05) effect on basal plasma levels of oGH, oPRL or oTSH.