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HUMAN CHORIONIC GONADOTROPIN MODULATES VASCULAR PERMSELECTIVITY IN THE PREOVULATORY RAT OVARY.
Mitsube, Kenrokuro1, Brännström, Mats2, Haraldsson, Börje3, 1 2 3
ABSTRACT- The passage of solutes from the ovarian blood vessel to the follicular compartment is restricted by the so-called blood follicle barrier. Increased permeability and changes in the permselectivity of the blood follicle barrier, observed after the LH-surge, have been suggested to be important for the normal ovulatory process. The aim of this study was to characterize the size selective properties of the rat ovarian vasculature during the preovulatory period. Immature female Sprague-Dawley rats, pretreated with PMSG (10 IU), were injected with hCG (10IU). Ovarian samples were taken before hCG administration (0 h) or 30 min, 1 h, 2 h, 4 h and 8 h after hCG. FITC-labeled Ficoll (0.8mg/rat) was injected 10 min before the ovarian sampling, and the distribution of Ficoll was measured in plasma and ovarian extracts. The Ficoll data were analyzed according to a two-pore model. The small pore radius (rS) of the ovarian vasculature before hCG was 54.7±1.2 
. The stimulation with hCG increased rS, which was significant at 2 h time point (62.3±0.8 ), then rS slowly declined to 57.1±1.2 at 8 h. The large pore radius (rL) at 0 h was 149.3±5.3 . While there was a tendency of increase in rL after hCG administration, no significant differences in rL were observed between unstimulated ovaries and gonadotropin-stimulated ones. The large pore fraction of the total hydraulic conductance (LpS%) significantly increased at 2 and 4 h after hCG injection, rising from 31% to 45% at both 2 and 4 h time points. These results indicate that the permselectivity of the ovarian blood-follicle barrier is modulated by LH/hCG, at least in part, through the changes in size and distribution of bimodal pores of the vascular wall.
KEY WORDS: ovary, vascular, permeability, pore