INHIBITION BY SOMATOSTATIN OF THE GROWTH-HORMONE, BUT NOT CORTICOTROPIN RESPONSE TO ANGIOTENSIN-II IN NORMAL MEN

The effect of an i.v. infusion of somatostatin (SRIH) (4.1 mu g/min/18 0 min) on angiotensin II (ANG II infusion for 60 min of successively i ncreasing doses of 4, 8 and 16 ng/kg/min; each dose for 20 min)-stimul ated growth hormone (GH) and corticotropin (ACTH) release was studied in 7 normal men. In addition, 7 additional normal subjects were tested with ANG II alone (as described above), GH-RH (0.1 mu g/kg body weigh t as an i.v. bolus) alone or the combination of GH-RH and ANG II. The ACTH response to ANG II was not modified by SRIH infusion; in contrast , the GH response to ANG II was significantly reduced by the concomita nt treatment with SRIH. On the other hand, the administration of GH-RH together with ANG II produced peak GH levels comparable to the sum of the individual responses to ANG II and GH-RH, given alone. These find ings provide evidence that the stimulatory effect of ANG II on GH, but not ACTH secretion, is under the inhibitory control of somatostatin, suggesting an interaction between ANG II and SRIH in regulation of GH secretion.