Modulatory role of eicosanoids in vascular changes during the preovulatory period in the rat

Abstract

Previous studies have demonstrated the involvement of eicosanoids (prostaglandins and hydroxyperoxides, including leukotrienes) in ovulation in several mammalian species. In this study, the role played by eicosanoids in the vascular changes that occur in the immediate preovulatory period after human chorionic gonadotropin (hCG) stimulation was examined in the rat. Changes in the ovarian uptake of two iodinated proteins were examined 30 minutes after i.v. injection of 125I-bovine serum albumin (BSA, Mr = 68,000) and 125I-alpha 2-macroglobulin (alpha 2M, Mr = 750,000). Uptake was measured during 30 min, 0, 3, 6, and 9 h after induction of ovulation by an i.p. injection of human chorionic gonadotropin (hCG, 10 IU). hCG enhanced the uptake of both iodinated proteins, with peak uptake values at 6 and 9 h. Intra-bursal injections of an ovulation inhibiting dose (0.5 mg/bursa) of indomethacin-a cycooxygenase inhibitor-and nordihydroguaiaretic acid (NDGA), esculetin, or caffeic acid--inhibitors of lipoxygenase--concomitantly with hCG attenuated the action of the hormone on 125I-BSA uptake. Indomethacin and esculetin were without effect on the uptake of alpha 2M. Ovarian and follicular blood flow was measured using 113Sn-microspheres. hCG increased ovarian and follicular blood flow with the most pronounced effect at the early time of 1.5 h. Indomethacin and NDGA did not attenuate this action of hCG. Accordingly, ovarian vascular resistance was reduced by hCG at 1.5, 6, and 9 h post-hCG, respectively, and indomethacin and NDGA had no significant effects. We suggest that one way in which eicosanoids are involved in follicular rupture is by their modulation of vascular permeability as revealed by uptake of the protein marker albumin.

Perfusion of the rat ovary: Application of pulsed arterial spin labeling MRI

“…A similar ratio between ovarian and kidney perfusion was determined previously using radioactive microspheres (36). A number of previous studies noted the high perfusion of the ovary and the steep increase in perfusion, capillary density, and blood content after hCG, as well as the subsequent decrease in perfusion after ovulation and during the luteal phase, as we observed here by MRI (23,(37)(38)(39). The short T 1 relaxation measured here for the ovary may reflect the high perfusion of this organ.…”

“…Arterial flow velocity may be influenced by the resistance to flow provided by the capillary bed. During the ovarian cycle, large changes are expected, not only in capillary density due to angiogenesis (1,3) but also in capillary resistance (29,38). Vasodilation and increased permeability change dramatically through the ovarian cycle, due to the activity of vascular endothelial growth factor (2,3,17,21) as well as the local release of nitric oxide (40) and prostaglandins (41).…”

Spatio-temporal analysis of vascular endothelial growth factor expression and blood vessel remodelling in pig ovarian follicles during the periovulatory period

“…An increase in ovarian blood flow and hyperaemic changes, elicited by the LH surge, were first observed by Zondek et al (1945). Changes in ovarian and follicular microcirculation have been quantified more recently by using immunohistochemical approaches (Murdoch & Dunn 1983, Abisogun et al 1988 as well as transrectal colour Doppler ultrasonography (Acosta et al 2003(Acosta et al , 2004. This non-invasive technique allowed conformation of an impressive increase in the ovarian blood flow that starts during the periovulatory period and stabilizes in mature CL.…”

Follicular microvasculature in the porcine ovary

“…These findings are similar to those in unstimulated rabbits Macchiarelli 2000) and support those reported previously in other animals. Studies on the non-invasive evaluation of ovarian and follicular blood flow in women by transvaginal color Doppler ultrasonography (Abisogun et al 1988;Blasco et al 1975;Janson 1975;Lee and Novy 1978;Murdoch et al 1983) have revealed marked regional differences in follicular blood flow with sustained increases in the basal and lateral walls of preovulatory follicles and concomitant decreases in the flow to their apical regions (Brannstrom et al 1998). These vascular changes are probably necessary for follicle rupture as has been suggested on the basis of in vivo (Brannstrom et al 1997) and in vitro (Bonello et al 1996;Lofman et al 1989) studies in the rat.…”