Leukocyte behaviour and permeability in the rat mesenteric microcirculation following induction of ovulation

Ovarian hyperstimulation syndrome (OHSS), a highly dangerous and incompletely understood complication of ovulation induction with exogenous gonadotrophins, can include haemoconcentration, hypovolaemia, hypotension, acute renal insufficiency, thromboembolism and ultimately death. Using intravital microscopy, we examined microvascular permeability and leukocyte-endothelial cell interactions in the rat mesenteric microcirculation associated with induction of ovulation.

In female rats treated with hMG and hCG, mesenteric venules were observed by intravital microscopy assisted by a video imager. Erythrocyte velocity was monitored, and rolling and adhesion of leukocytes were studied by transmission video images. Transvascular leakage of fluorescein isothiocyanate-labelled albumin was assessed by epi-illumination.

Administration of hMG and hCG significantly increased vascular protein leakage within a few hours, and also reduced rolling velocities of leukocytes in venules and increased numbers of leukocytes adherent to endothelium at 16 h following hCG injection. The administration of antibodies against intracellular adhesion molecule (ICAM)-1 inhibited these reactions.

By induction of ovulation, vascular permeability is increased not only at the surface of the ovary but also in the mesentery. Alteration of leukocyte behaviour in the microcirculation through mechanisms involving ICAM-1 is one likely cause of the protein leakage.