The effect of intra-aortic infusion of prostaglandin E-2 on luteal function of mid-cycle heifers

Different actions of noradrenaline and nitric oxide on the output of prostaglandins and progesterone in cultured bovine luteal cells

The effects of noradrenaline (NA) and nitric oxide (NO) on prostaglandins (PGs) and progesterone (P4) secretion during the development of the bovine corpus luteum (CL) were investigated. Bovine luteal cells of early and mid-cycle CL were cultured for 20 to 24 h in medium containing 10% calf serum, washed, and treated with NA or nitrergic agents for an additional 16 h in a serum-free medium. NA (10(-5) M) stimulated P4 from early and mid-cycle CL by 238% and 154% (P < 0.01), respectively. Moreover, although NA induced a twofold increase in PGE2 secretion (P < 0.01) in both examined periods, the effect of NA on PGF2alpha secretion was approximately 1.5 times higher (P < 0.05) in early than in mid-cycle CL. Two NO synthase inhibitors, L-NAME and L-NOARG (both 10(-4) M), stimulated P4 secretion only in mid-luteal cells (P < 0.01), although they did not affect the cells from early CL. Although a NO donor, S-NAP (10(-4) M) inhibited P4 secretion from mid-cycle luteal cells (P < 0.05), it strongly stimulated PGE2 in both examined phases (P < 0.001). On the other hand, the output of PGF2alpha was stimulated by S-NAP only in the cells of the mid-cycle CL (P < 0.01). The overall results suggest that adrenergic and nitrergic agents play opposite roles in the regulation of bovine CL functions. Whereas NA may play a supporting role in luteal development, NO may participate in the functional regression of the bovine CL by inhibiting steroidogenesis.

Prostaglandin F2 alpha, progesterone and oxytocin production by cultured bovine luteal cells treated with prostaglandin E2 and pregnancy-specific protein B

The objectives of this experiment were to study the effects of pregnancy-specific protein B (PSPB) and prostaglandin E2 (PGE2) on bovine luteal cell progesterone (P4), prostaglandin F2 alpha (PGF2 alpha) and oxytocin production. Corpora lutea were collected during the mid- (days 10-12; n = 5) or late-luteal (days 17-18; n = 5) stages of the estrous cycle. Luteal cells were dispersed and accessory cells removed. Luteal cells (1.5 x 10(5)) were incubated in a 3 x 3 factorial arrangement and treated with PSPB (0, 2.5, or 5.0 micrograms) and PGE2 (0, 100, or 200 ng) in 500 microL of Ham's F-12 medium. All cells were incubated for 18 h before adding treatments. Samples were then collected at 6 h and 12 h. During the 18 h pretreatment period, P4, PGF2 alpha, and oxytocin production was similar between the prospective treatment groups. The PSPB failed to increase P4 production. The PGE2 x time interaction showed that P4 increased in response to PGE2 treatment at 6 h (P < 0.001) and 12 h (P < 0.03). Also, the stage x time interaction indicated that mid-stage cells produced more (P < .001) P4 than late-stage cells during the pretreatment period at 6 h and 12 h. The PSPB did not alter PGF2 alpha production by mid-stage cells, but increased (P < .05) PGF2 alpha by late-stage cells. Also, PGE2 stimulated (P < 0.001) PGF2 alpha secretion by both mid- and late-stage cells; luteal cells treated with 200 ng of PGE2 produced more (P < 0.001) PGF2 alpha than 100 ng of PGE2. Oxytocin secretion was not changed by treatment with PGE2 or PSPB. Oxytocin production was greater (P < 0.001) by mid-stage than late-stage cells during the pretreatment period at 6 h and 12 h. Oxytocin production was similar between the 6 h and 12 h culture times within stage of the cycle. These data indicate that PSPB does not change bovine luteal cell P4 or oxytocin production, but elevates PGF2 alpha in late-stage cells. The PGE2 increases both P4 and PGF2 alpha, but does not alter oxytocin production. Lastly, PSPB and PGE2 do not interact to promote P4 PGF2 alpha, or oxytocin production by cultured bovine luteal cells.

Intrauterine infusion of prostaglandin E2 and subsequent luteal function in cattle

The objective was to evaluate the effect of intrauterine infusion of prostaglandin E2 (PGE2) on luteal function in cattle. Heifers and cows were randomly assigned after two normal estrous cycles to either PGE2 or control treatment groups. Females in Treatment A were infused with 1 mg of PGE2 once daily into the uterine horn ipsilateral to the corpus luteum between days 7-10 of the estrous cycle with a 0.25 ml plastic semen straw and an artificial insemination pipette. Females in Treatment B were similarly infused with 1 mg of PGE2 once daily in 20 ml of a carrier vehicle via a catheter on days 10 and 11 of the estrous cycle. Control animals were infused with the carrier vehicle using either a semen straw (Treatment C) or via a catheter (Treatment D) on the same days of the estrous cycle. Blood samples were collected daily to monitor plasma progesterone concentrations during the treatment period. Females infused with PGE2 on days 7-10 of the estrous cycle returned to estrus in a mean of 23.5 days (range 22-25 days) and were similar (P > 0.05) to those infused on days 10 and 11 which returned to estrus in 23.5 days (range 22-25 days). Animals similarly infused with carrier vehicle on the same days of the estrous cycle returned to standing estrus in 20.2 days (range 17-23 days). Plasma progesterone concentrations indicated an extended period of elevated progesterone concentrations in PGE2-treated animals compared with control animals. These results indicate that short term administration of PGE2 early in the estrous cycle may result in extended luteal maintenance.