Fallopian Tube Microvasculature in the Rabbit

Abstract

Summary, the microvascular architecture of rabbit Fallopian lube isthmic, ampuliary and fimbrial regions was examined by the corrosion vascular caslscanning electron microscope method. The aorla and inferior vena cava of virgin adult female rabbits (25-3-5 kg) were cannulated; after blood wash oul. methacrylate casting medium was infused via the aorta. After plastic hardening. Fallopian lubes were excised, tissues corroded and casts prepared for scanning electron microscopy. The isthmic myosalpinx is encircled subserosally by an interlocking venous plexus. We suggest that a rise in pelvic venous pressure could lead to a decrease in isthmic luminal diameter nnd thus act as a sphincter contributing to the known delay in ovum transport at the ampuliary isthmic junction. Stereo pairs of photomicrographs showed that isthmic plicae are supplied by arterioles which change little in diameter passing through the tubal wall. Near the apex of a fold, these arterioles terminate in a subepithelial capillary plexus which drains to deep mucosal and plical core venules. In contrast, the ampulla is supplied by smaller and less frequent arterioies. Frequent large venules extending high into the plicae drain the subepithelial capillary plexus. Based on this microvascular architecture, we suggest that the subepithelial capillary plexus of the apical region of the plicae probably contains high pressure blood in the isthmus and lower pressure blood in the ampulla. Therefore, plicae in these regions may be specialised for net luminal fluid secretion and absorption respectively, implying a role for the microvasculature in tubal transport by initiation or modification of fluid flow along the lumen.

Microvascular Architecture of the Pregnant Rabbit Oviduct

“…lb) [Verco et al, in press]. This contrasts markedly with our current observations in pregnant rabbits and observations of control oviduct MVA [Verco et al, 1983a]; that there are any changes in tubal MVA at all in pregnancy and after ovariectomy implies a relationship between tubal microvasculature and local or circulating ovarian and placental hormones. Greiss and Anderson [1970] reported that estradiol caused marked uterine vasodilation in ewes (although during prolonged administration resistance developed); progesterone seemed to sensitize the vascular bed to estradiol.…”

“…The changes observed in fimbrial core MVA in this study which contrast so markedly with control fimbrial core MVA [Verco et al, 1983a] and that reported after ovariectomy [Verco et al, in press] suggest a particular sensitivity of tubal microvasculature to ovarian or pla cental hormones and. using a similar argument to that developed above, indicates the potential for fimbrial venous distension around the time of ovulation.…”

“…Around the time of ovulation known varia tions in rabbit ovarian venous estradiol and proges terone [Hilliard and Eaton, 1971] and tubal estradiol and progesterone receptor binding [El Banna and Sacher, 1977] may be associated with changes in tubal venous distension similar to those observed in preg nancy. The relationship between ovarian or placental hormones and tubal microvasculature implied by this study, and by investigation of tubal MVA after oophorectomy [Verco et al, in press], is of particular interest when considering the proposal that variations of isthmic subserosal venous pressure or tone may be relevant in tubal transport [Verco et al, 1983a]. It was suggested that a rise in isthmic subserosal venous pressure or fall in isthmic subserosal venous tone would be associated with isthmic occlusion [Verco et al, 1983a] and could thus account for the observed delay in tubal ovum transport at the ampullary-isthmic junction [Pauerstein et al.…”

“…Analysis of rabbit uterine tube microvascular architecture (MVA) using the vascular corrosion cast scanning electron microscope (SEM) technique has led to speculation on the role of tubal MVA in gamete transport [Verco et al, 1983a]. A decrease in the size and number of the characteristic large ampullary plical and fimbrial veins observed in rabbit tubal MVA 4 weeks after ovariectomy, led Verco et al [in press] to suggest that the reported tubal dysfunction following oophorectomy may have a vascular component.…”

Uterine Tube Microvascular Architecture after Oophorectomy in the Rabbit

“…Verco et al [1983] described the rabbit uterine tube microvascular architecture (MVA) and speculated on the role of the tubal microvas culature in tubal gamete transport; they sug gested that the large interlocking isthmic subserosal vascular plexus had the potential, if distended, to act as an extramyosalpingeal sphincter. In addition, they proposed that the large and frequent ampullary plical veins may indicate a large local capacity for inter stitial and perhaps also ampullary luminal fluid absorption which could modify fluid flow along the tube.…”