Effect of arginine and ornithine infusions on luteinizing hormone secretion in prepubertal ewes.

Abstract

Although activation of the hypothalamic GnRH pulse generator is known to initiate the onset of puberty in immature animals, the metabolic cues by which information about the stage of body growth and development are translated into central nervous activity remain obscure. In the present study, the function of L-arginine (ARG) or L-ornithine (ORN) as promoters of pulsatile LH secretion was investigated in 2-mo-old prepubertal ewes. Suffolk ewe lambs (n = 17) fitted with intrajugular catheters were divided into three groups. Saline (200 mL) was infused for 1 h into all lambs. In Group 1, saline infusion was continued for another hour. In Group 2, 200 mL of an ARG solution (350 mM, pH 7.4) was infused for 1 h, and in Group 3, ORN was infused (200 mL, 350 mM, pH 7.4) for 1 h. Blood samples were collected at 15-min intervals from 60 min before until 285 min after the end of infusions. The Pulsar program was used to identify significant LH episodes during 285 min after infusions. Mean LH concentrations during the 285-min period after infusion were greater (P < .05) in Group 2 than in Groups 1 and 3. The mean LH pulse frequencies and amplitudes did not differ among the groups. However, in lambs infused with ARG, 13 of their 17 LH pulses had amplitudes > 1 ng/mL, whereas in control ewes only 5 of 20 pulses had amplitudes > 1 ng/mL. All of the ARG-infused ewes had two or more LH pulses with amplitudes > 1 ng/mL; only 1 of 6 control lambs had two pulses. Results indicate that ARG stimulates LH secretion in prepubertal ewes.

Pituitary and testis responsiveness of young male sheep exposed to testosterone excess during fetal development

“…One or two days before GNRH analog testing, indwelling catheters were placed in both jugular veins under local anesthesia as described previously (Recabarren et al 1995). Blood sampling was performed to acclimatize the males to the procedures and to review the patency of the catheters.…”

Degradation of L-arginine and N-carbamoyl glutamate and their effect on rumen fermentationin vitro

“…As a precursor of polyamines and nitric oxide (NO), ARG could improve nitrogen metabolism, angiogenesis and lactogensis (Morris, 2006;Kim and Wu, 2009). L-arginine supplementation increases milk production in cattle and growth hormone in sheep (Chew et al,1984;Davenport et al, 1990aDavenport et al, , 1990b, plasma flow in the portal and hepatic veins in steers (Maltby et al, 2005), and stimulates the production of luteinizing hormone in prepubertal ewes (Recabarren et al, 1996). Recently, injected Arg-HCl has decreased embryonic loss in ewes (Luther et al, 2008), increased lamb birth weight in gestationally nutrient restricted ewes (Lassala et al, 2010), and improved fetal lamb survival to term in prolific ewes (Lassala et al, 2011).…”

Effects of arginine, growth hormone-releasing hormone (GHRH) and neostigmine administered singly or in paired combinations on growth hormone (GH) release in pigs

“…Chez l'homme, l'arginine (ARG) induit une sécrétion d'hormone de croissance, probablement via une diminution du tonus somatostatinergique. Pour déterminer le méca-nisme par lequel l'ARG influence la sécrétion de GH chez le porc, les effets sur la GH plasmatique de l'ARG (1 g/kg de poids vif, infusée de -15 à -5 min), du growth hormone-releasing hormone (GHRH, 2 pg/kg, à 0 min) et (Davenport et al, 1990a(Davenport et al, , 1995, adult sheep (Hertelendy et al, 1969(Hertelendy et al, , 1970Davis and Borger, 1973;Kuhara et al, 1991;Recabarren et al, 1995) and cattle (Vicini et al, 1988;Davenport et al, 1990b). Little is known about the effect of ARG on GH secretion in pigs.…”

“…Ornithine elicits GH secretion in sheep (Davenport et al, 1990a(Davenport et al, , 1995Recabarren et at, 1995). Glutamic acid is able to stimulate GH release in pigs (Barb et al, 1996).…”