Summary. Plasma concentrations of progesterone and 17α-hydroxyprogesterone were high in the 2nd and 3rd months of gestation, but 20α-dihydroprogesterone increased from a level of 2 ng/ml, during the first 3 months, to 10–15 ng/ml during months 5–10, to reach 80–120 ng/ml during the last 30 days before foaling.
E. Seren, C. Tamanini, R. Gaiani and G. Bono
G Galeati, M Spinaci, N Govoni, A Zannoni, P Fantinati, E Seren and C Tamanini
The aim of this study was to investigate the effect of fasting on both vascular endothelial growth factor (VEGF) production and VEGF mRNA expression in growing ovarian follicles (>5 mm in diameter) from gilts at 48 h after equine chorionic gonadotrophin (eCG) treatment. The concentrations of VEGF and albumin were measured in the follicular fluid of single follicles, and VEGF mRNA was determined in the follicle wall. Fasting resulted in a significant increase in VEGF concentrations in follicular fluid (20.64+/-0.72 versus 10.79+/-0.86 ng ml(-1), P<0.001), but it did not affect the total amount of VEGF mRNA in the follicle wall compared with that of fed animals. However, VEGF mRNA in the theca and granulosa compartments increased and decreased, respectively, compared with that of fed animals. The concentrations of albumin measured in follicular fluid as an index of vessel permeability were higher in fasted than in animals fed normally, most likely as a result of the increased VEGF production. Follicular steroidogenesis was impaired in fasted animals. Progesterone was the most abundant steroid in the follicular fluid and oestradiol was present in lower concentrations, thus indicating an alteration in the steroidogenic enzymatic cascade. In conclusion, fasting induces an increase in both VEGF production and vessel permeability. Such a reaction is unable under severe food deprivation to preserve follicle function, but may represent a mechanism that regulates blood vessel extension and distribution in relation to tissue requirements and availability of systemic nutrient.