Local Changes in Blood Flow Within the Early and Midcycle Corpus Luteum after Prostaglandin F2α Injection in the Cow1

Abstract

One of the postulated main luteolytic actions of prostaglandin (PG) F(2 alpha) is to decrease ovarian blood flow. However, before Day 5 of the normal cycle, the corpus luteum (CL) is refractory to the luteolytic action of PGF(2 alpha). Therefore, we aimed to determine in detail the real-time changes in intraluteal blood flow after PGF(2 alpha) injection at the early and middle stages of the estrous cycle in the cow. Normally cycling cows at Day 4 (early CL, n = 5) or Days 10--12 (mid CL, n = 5) of the estrous cycle (estrus = Day 0) were examined by transrectal color and pulsed Doppler ultrasonography to determine the blood flow area, the time-averaged maximum velocity (TAMXV), and the volume of the CL after an i.m. injection of a PGF(2 alpha) analogue. Ultrasonographic examinations were carried out just before PG injection (0 h) and then at 0.5, 1, 2, 4, 8, 12, 24, and 48 h after the injection. Blood samples were collected at each of these times for progesterone (P) determination. The ratio of the colored area to a sectional plane at the maximum diameter of the CL was used as a quantitative index of the changes in blood flow within the luteal tissue. Blood flow within the midcycle CL initially increased (P < 0.05) at 0.5-2 h, decreased at 4 h to the same levels observed at 0 h, and then further decreased to a lower level from 8 h (P < 0.05) to 48 h (P < 0.001). Plasma P concentrations decreased (P < 0.05) from 4.7 +/- 0.5 ng/ml (0 h) to 0.6 +/- 0.2 ng/ml (24 h). The TAMXV and CL volume decreased at 8 h (P < 0.05) and further decreased (P < 0.001) from 12 to 24 h after PG injection, indicating structural luteolysis. These changes were not detected in the early CL, in which luteolysis did not occur. In the early CL, the blood flow gradually increased in parallel with the CL volume, plasma P concentration, and TAMXV from Day 4 to Day 6. The present results indicate that PGF(2 alpha) induces an acute blood flow increase followed by a decrease in the midcycle CL but not in the early CL. This transitory increase may trigger the luteolytic cascade. The lack of intraluteal vascular response to PG injection in the early CL appears to be directly correlated with the ability to be resistant to PG.

Excess estrogen sulfoconjugation as the possible cause for a poor sign of parturition in pregnant cows carrying somatic cell clone fetuses

“…E 1 concentration was measured by the EIA technique, as described by Acosta et al (2002). Dilutions of anti-estrone-3-glucuronide-BSA IgG (anti-E 1 ; Cosmo Bio Co., Ltd, Tokyo, Japan) and estrone-3-carboxymethyl ether-horseradish peroxidase (CME-HRP) (Cosmo Bio) were 150 000 and 70 000 respectively.…”

Local interaction of prostaglandin F2α with endothelin-1 and tumor necrosis factor-α on the release of progesterone and oxytocin in ovine corpora lutea in vivo: a possible implication for a luteolytic cascade

“…Substances infused through the MDS act in the local microenvironment around the capillary membrane. Thus, the model used here does not have any major effect on the constriction of blood vessels in the whole CL, and hence excludes a direct effect on the vasoconstriction that was shown to be a crucial process for luteolysis (Niswender et al 1976, Azmi & O-Shea 1984, Knickerbocker et al 1988, Acosta et al 2002. In this context, the present in vivo data may give basic and important information on the interaction of PGF 2a with ET-1 and TNFa in the cascade of functional luteolysis.…”

Cloning of a buffalo (Bubalus bubalis) prostaglandin F2α receptor: changes in its expression and concentration in the buffalo cow corpus luteum

“…The expression of mRNA encoding prostaglandin endoperoxide G/H synthase-2 is decreased in the early luteal phase while it is increased in the mid-luteal phase following PGF 2a treatment (Tsai & Wiltbank 1998). Also, there appears to be a distinct haemodynamic change in response to PGF 2a injection between the early (no change in blood flow) and mid-luteal (decreased blood flow) phases (Acosta et al 2002). There is increasing evidence to suggest that intraluteal PGF 2a production appears to be one of the key factors that determines the luteolytic effect of exogenously administered PGF 2a (reviewed by Diaz et al 2002).…”