Vasoactive intestinal polypeptide and endometrial blood flow in the goat

Endometrial blood flow was measured in seven goats twice before, once during, and twice after the close intra-arterial infusion of 300 pmol/min of vasoactive intestinal polypeptide (VIP). A saline solution of ⁸⁵krypton was injected intra-arterially and local blood flow calculated from the disappearance rate of the isotope from tissue surrounding a miniature Geiger-Müller probe in the uterine lumen. Initial blood flows (median and range) in animals pretreated with oestradiol-17β (N = 4) or with a regimen of oestradiol-17β and progesterone (N = 3), respectively, were 0.21 (0.11–0.35) and 0.20 (0.06–0.27) ml min^?1 g^?1. No significant change in endometrial blood flow occurred during or after the infusion of VIP, although the dose was sufficient to increase heart rate from 2.14 ± 0.15 to 2.32 ± 0.16 Hz (P < 0.001). The results indicate that VIP, in a dose known to increase myometrial blood flow in goats, is unable to evoke vasodilatation in the endometrium of this species. Since there is a corresponding variation in the density of nerve fibers containing VIP, it is suggested that VIP may play a role in regulating the partition of uterine blood flow in goats.