In utero glucocorticoid exposure reduces fetal skeletal muscle mass in rats independent of effects on maternal nutrition.

Maternal stress and undernutrition can occur together and expose the fetus to high glucocorticoid (GLC) levels during this vulnerable period. To determine the consequences of GLC exposure on fetal skeletal muscle independently of maternal food intake, groups of timed-pregnant Sprague-Dawley rats (n = 7/group) were studied: ad libitum food intake (control, CON); ad libitum food intake with 1 mg dexamethasone/l drinking water from embryonic day (ED)13 to ED21 (DEX); pair-fed (PF) to DEX from ED13 to ED21. On ED22, dams were injected with [(3)H]phenylalanine for measurements of fetal leg muscle and diaphragm fractional protein synthesis rates (FSR).

Reduced hypothalamic neuropeptide Y expression in growth hormone- and prolactin-deficient Ames and Snell dwarf mice.

Neuropeptide Y (NPY)-producing neurons in the hypothalamic arcuate nucleus (ARC) have been implicated in GH feedback in several studies in rats. Ames (df/df) and Snell (dw/dw) dwarf mice carry mutations in transcription factors Prop-1 and Pit-1, respectively, that abrogate detectable expression of GH, prolactin, and TSH. The present study was undertaken to determine whether and to what extent hypothalamic NPY neurons are affected by the lifelong absence of pituitary hormone feedback in hypopituitary Ames and Snell dwarf mice.