UTERINE EXTRACELLULAR FLUID VOLUME AND BLOOD-FLOW AFTER ARTIFICIAL UTERINE STIMULATION TO RATS DIFFERENTIALLY SENSITIZED FOR THE DECIDUAL CELL REACTION

Uterine extracellular fluid volume (ECFV) and blood flow (BF) were assessed after unilateral intrauterine injection of sesame oil to rats given either ideal sensitization for the decidual cell reaction or one of several forms of non-ideal sensitization. The study was intended to determine how changes in uterine ECFV and BF might contribute to the Evans blue dye reaction that can be elicited during early decidualization. Uterine ECFV was determined by the uterine volume of distribution of Cr-51-EDTA after its i.v. injection; BF was determined by the radioactive microsphere technique. ECFV was significantly greater in oil-injected than in control horns by 8 h after deciduogenic stimulation, reaching a maximum of 0.63 +/- 0.06 mul/mg (p < 0.05) in oil-injected horns at 16 h. Ideal temporal sensitization and sensitization with estrogen both were essential to obtain the significantly increased ECFV in stimulated horns. Although absolute uterine BF increased to oil-injected horns, the increase matched uterine weight gains, making relative uterine BF similar for both horns (3-4 mul/min/mg) at all times after unilateral deciduogenic stimulation. Ideal sensitization did not significantly alter the relative uterine BF. The increase in ECFV occurs at a similar time and requires the same ideal sensitization as the stimulation-induced increase in endometrial vascular permeability described previously, suggesting that these events are under similar control. We suggest that enzymatic changes to the uterine extracellular matrix may contribute to the Evans blue reaction by creating a larger compartment into which protein-dye complexes may diffuse. The absence of increased relative uterine BF after deciduogenic stimulation and after ideal sensitization does not exclude the possible importance of a high basal BF in this phenomenon.