Nitric anterior pituitary

In the rat anterior pituitary gland, nitric oxide synthase is present in gonadotrophs and in foUiculo-stellate cells (Ceccatelli et al. 1993). Castration and ovariectomy, respectively, resulted in markedly increased nitric oxide synthase mRNA levels. In the male rat a small, but not significant, increase was seen 12 h after surgery, whereas at 3 h levels were still similar to sham-operated rats. After 24 h there was a > 3-fold increase in mRNA levels, and this remained elevated for 14 days, the longest period studied. Also in the female rats, there was a clear but less strong increase at 4 and 14 d after ovariectomy. Substitution treatment with testosterone or estrogen completely prevented these increases in male and female rats, respectively. 

Combined immunohistochemical, in situ hybridisation, and biochemical studies by Ceccatelli et al. (1993) provided evidence for nitric oxide synthase synthesis in the foUiculo-steUate cells that do not produce any known hormones (Horvath and Kovacs 1988) but may indirectly influence growth-hormone secretion. % interferon-y Vankelecom et al. (1997) induced nitric oxide synthase (iNOS) in subpopulation of folliculo-stellate cells and in an unidentifiable population in monolayer cultures of the rat anterior pituitary. 

Treatment of Pll cells, derived from the transplantable rat pituitary tumour 7315a, with inter-feron-Y (50U/ml) and lipopolysaccharide (10 ig/ ml) resulted in a 23-fold increase in nitrite production and induced expression of iNOS protein (Xu and Miller 2000). The increase in nitrite levels was attenuated by the non-selective nitric oxide synthase (NOS) inhibitor hl -nitro-L-arginine methyl-ester, but not the neuronal NOS inhibitor 7-nitro-imidazole. Incubation of rat anterior pituitaries with either N -monomethyl-L-arginine or N -nitro-L-arginine methylester significantly increased prolactin release (Duvilanski et al. 1995). 

Vankelecom H, Matthys P, Denef C. Involvement of nitric oxide in the interferon-gamma-induced inhibition of growth hormone and prolactin secretion in anterior pituitary cell cultures. Mol Cell Endocrinol 1997 129 157-167. 

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