Changes of Progesterone and Endothelin Concentrations in the Peripheral Plasma of Female Calves and Cycling Cows: Effects of PGF2.ALPHA. Injection.

Abstract

Abstract. It is well known that an injection of prostaglandin F2α (PGF2α) or its analogue during the mid luteal phase of the estrous cycle induces a rapid decrease in plasma progesterone (P4) concentration, followed by luteolysis in the cow. There is evidence that a potent vasoactive peptide, endothelin-1 (ET-1), is produced in the bovine corpus luteum (CL), and that it is directly involved in luteolysis. We previously found that ET-1 concentrations in the peripheral plasma increase during the period of luteolysis and ovulation in cows. However, it is not clear whether the elevation of peripheral plasma ET-1 concentration observed during luteolysis and ovulation originates exclusively from the ovary and/or CL. Such a profile of plasma ET-1 concentration may be affected by the age of female calves as well as the activity of the ovary. Thus, we aimed to 1) determine in detail the changes in plasma ET-1 and P4 concentrations during the estrous cycle in the cow, 2) investigate plasma changes in ET-1 and P4 concentrations in new-born, 120-day-old and 240-day-old female calves, and 3) examine the effect of luteolytic injection of PGF2α analogue on the plasma ET-1 concentrations in the animals in this study. The peripheral plasma ET-1 concentrations in the cycling cows showed a pulsatile increase. They reached the their highest level (13.66 pg/ml) around the time of luteolysis and estrus, dropped significantly during Days 2-12 (early to mid luteal phase) and Days 13-19 (late luteal phase) (p<0.05), and then increased again on Days 20-22 (p<0.05) when the next estrus appeared. In the peripheral plasma of newborn, 120-day-old and 240-day-old female calves, P4 concentrations remained at low levels (0.1-0.2 ng/ml). ET-1 concentrations in these animals were lower than those in the cycling cows, and remained at low levels throughout the experimental period. Moreover, plasma ET-1 concentrations, unlike those in the cycling cow, did not change after a luteolytic PGF2α injection. In conclusion, the results of the present study gave the first detailed information that plasma ET-1 concentrations increase in a pulsatile manner after the onsets of spontaneous luteolysis and PGF2α-induced luteolysis in cycling cows, but not in female calves. The results suggest that the changes in the plasma ET-1 concentrations during the estrous cycle directly correlate with the cyclic changes in the ovarian function and the uterus.

Evaluación y entrenamiento funcional en el adulto mayor

“…However, such a change was not observed following the injection of PGF2␣ in the early CL. The absence of this change within the early CL, in which luteolysis did not occur, and the progressive vascular changes in the midcycle CL, in which luteolysis did occur, suggest that these vascular alterations are stage and PG dependent and are necessary for the induction of the local release of ET-1 (Ohtani et al, 1998;Levy et al, 2000) and Ang II (Ohtani et al, 2001), which further induce a decrease in the blood supply (flow) as a result of vasoconstriction. The initial acute increase in intraluteal blood flow at 0.5-2 h after PGF2␣ injection may be crucial for stimulating luteal endothelial cells to produce and release vasoactive substances necessary to trigger the cascade of changes leading to luteolysis.…”

“…Moreover, these vasoactive peptides have been shown to modify the synthesis and secretion of hormones produced in ovarian cells in an autocrine/paracrine manner (Kamada et al, 1992;Yoshimura et al, 1993;Johnson et al, 1994;Tedeschi et al, 1994;Acosta et al, 1998). The high concentrations of Ang II, ET-1 and ANP in the different follicular compartment (Kim et al, 1989;Gutkowska et al, 1993;Hagemann et al, 1994b;Acosta et al, 1998;Karam et al, 1999), the presence of their specific receptors (Saheki et al, 1989;Brunswig-Spickenheier and Mukhopadhyay, 1992;Tedeschi et al, 1994;Nielsen et al, 1995), and the cyclic variation in their ovarian activities during the estrous cycle (Kim et al, 1992;Hagemann et al, 1994a;Ohtani et al, 1998Ohtani et al, , 2001 suggest important roles for these vasoactive peptides in ovarian physiology. Recently, an active intraovarian endothelin-renin-angiotensin-atrial natriuretic peptide system has been postulated in rats (Usuki et al, 1993).…”