Prolactin secretion in hypothyroid endotoxemic rats: involvement of L-arginine and nitric oxide synthase.
The identification of nitric oxide (NO) within the hypothalamus and pituitary gland has suggested its role as modulator of the activity on hypothalamic-pituitary axis. Hypothalamic NO synthase (NOS) is known to be regulated by thyroid hormones. We investigated the effects of previous injection of N-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, and L-arginine (L-Arg), the substrate for NO synthesis, on prolactin (PRL) secretion, through the lipopolysaccharide (LPS)-induced inflammatory response in thyroidectomized (TX) rats. TX or sham-operated (N) rats were intraperitoneally (i.p.) injected with L-NAME (10 mg kg) or L-Arg (200 mg kg) or the same volume of vehicle (saline solution) 30 min before endotoxemia-induction with LPS at 250 mug (100 g body weight), i.p.. In N rats, NO increased PRL release in response to endotoxemia, whereas in hypothyroid rats, NO appeared to have the opposite effect. Our data support the hypothesis that NO exerts a modulatory influence on PRL secretion after LPS-induced inflammatory response.
Rodriguez
Tania T
TT
Department of Physiology, Health Sciences Center, Federal University of Bahia, 40110-100 Bahia, Brazil.
Biscarde
Eduardo F S
EF
Muniz
Relva F D G
RF
Amoedo
Maurício K
MK
Ramalho
Maria José
MJ
D000818:Animals; D001120:Arginine / Q000378:metabolism* / Q000494:pharmacology; D019446:Endotoxemia / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007037:Hypothyroidism / Q000378:metabolism*; D007249:Inflammation; D008070:Lipopolysaccharides / Q000378:metabolism; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D011388:Prolactin; D001120:Arginine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester