ラットにおけるPGE₂, 2-DGおよびL-arginineの視床下部GHRHおよびSRIFの放出に及ぼす影響とGH分泌との相関

抄録

The effects of prostaglandin E₂ (PGE₂), 2-deoxy-D-glucose (2-DG) and L-arginine on hypothalamic GHRH and SRIF release with respect to GH secretion were studied in conscious male rats.
Intracerebroventricular (icv) injection of 5/μg PGE₂ and intravenous (iv) infusion of 1g/kgBW L-arginine caused an increase in plasma GH levels, but icv (36/μg) or iv (400mg/ kgBW) injection of 2-DG suppressed spontaneous GH surge in conscious rats. The concentration of hypothalamic GHRH was decreased in all three groups of the animals, but the concentration of hypothalamic SRIF was decreased only in 2-DG-treated animals.
In the perifusion system using rat hypothalamus, PGE₂ (0.28μM, 2.8μM), 2-DG (22mM) and L-arginine (3mM) stimulated GHRH release from rat hypothalamus. 2-DG also stimulated SRIF release more predominantly than GHRH release.
Passive immunization with anti-GHRH serum inhibited the GH secretion induced by icy injection of 5μg PGE₂ and by iv infusion of 1g/kgBW L-arginine in conscious rats. In contrast, GH secretion induced by iv injection of 50μg/kgBW PGE₂ was not affected by the pretreatment with the antiserum.
These results suggest that the central effect of PGE₂ and peripheral effect of L-arginine to stimulate GH secretion are mediated by hypothalamic GHRH release, and that the inhibitory effect of 2-DG on GH secretion is predominantly mediated by hypothalamic SRIF release rather than GHRH release in rats.