Arginine Stimulates Growth Hormone Secretion by Suppressing Endogenous Somatostatin Secretion*

Abstract

To determine how arginine (Arg) stimulates GH secretion, we investigated its interaction with GHRH in vivo and in vitro. Six normal men were studied on four occasions: 1) Arg-TRH, 30 g arginine were administered in 500 mL saline in 30 min, followed by an injection of 200 micrograms TRH; 2) GHRH-Arg-TRH, 100 micrograms GHRH-(1-44) were given iv as a bolus immediately before the Arg infusion, followed by 200 micrograms TRH, iv; 3) GHRH test, 100 micrograms GHRH were given as an iv bolus; and 4) TRH test, 200 micrograms TRH were given iv as a bolus dose. Blood samples were collected at 15-min intervals for 30 min before and 120 min after the start of each infusion. Anterior pituitary cells from rats were coincubated with Arg (3, 6, 15, 30, and 60 mg/mL) and GHRH (0.05, 1, 5, and 10 nmol/L) for a period of 3 h. Rat GH was measured in the medium. After Arg-TRH the mean serum GH concentration increased significantly from 0.6 to 23.3 +/- 7.3 (+/- SE) micrograms/L at 60 min. TRH increased serum TSH and PRL significantly (maximum TSH, 11.1 +/- 1.8 mU/L; maximum PRL, 74.6 +/- 8.4 micrograms/L). After GHRH-Arg-TRH, the maximal serum GH level was significantly higher (72.7 +/- 13.4 micrograms/L) than that after Arg-TRH alone, whereas serum TSH and PRL increased to comparable levels (TSH, 10.2 +/- 3.0 mU/L; PRL, 64.4 +/- 13.6 micrograms/L). GHRH alone increased serum GH to 44.9 +/- 9.8 micrograms/L, significantly less than when GHRH, Arg, and TRH were given. TRH alone increased serum TSH to 6.6 +/- 0.6 mU/L, significantly less than the TSH response to Arg-TRH. The PRL increase after TRH only also was lower (47.2 +/- 6.8 micrograms/L) than the PRL response after Arg-TRH. In vitro Arg had no effect on basal and GHRH-stimulated GH secretion. Our results indicate that Arg administered with GHRH led to higher serum GH levels than did a maximally stimulatory dose of GHRH or Arg alone. The serum TSH response to Arg-TRH also was greater than that to TRH alone. We conclude that the stimulatory effects of Arg are mediated by suppression of endogenous somatostatin secretion.

Effect of <i>in ovo</i> injection with L-arginine on productive and physiological traits of Japanese quail

“…Campbell et al (2004) reported that it is well documented that the infusion of arginine stimulates growth hormone secretion from the anterior pituitary. This increase in growth hormone secretion has been attributed to the suppression of endogenous somatostatin secretion (Alba-Roth et al, 1988). Darras et al (1990;1992) indicated that during embryonic growth, liver cells are capable of responding to the growth hormone by converting T4 to T3 and decreasing type III iodothyronine deiodinase.…”

Plasma growth hormone (GH), insulin and amino acid responses to arginine with or without aspartic acid in pigs. Effect of the dose

“…This is believed to be due to their somatostatinergic hypertone [35]. ARG-induced GH release is probably mediated by a decrease in the somatostatinergic tone as demonstrated indirectly by the use of cholinesterase inhibitors in man [1,18,20] and pigs [10].…”

The arginine and GHRP-2 tests as alternatives to the insulin tolerance test for the diagnosis of adult GH deficiency in Japanese patients: A comparison

“…Insulin-induced hypoglycemia and arginine stimulate GH secretion by suppressing endogenous somatostatin secretion in the hypothalamus [14,15]. GHRP-2 is a potent synthetic GH secretagogue, which acts on a specific receptor at the hypothalamic arcuate nucleus-median eminence to potentiate GH-releasing activity [16,17].…”