Post-partum release of prostaglandin F(2alpha) and uterine involution in the cow.

Peripheral plasma levels of the main blood plasma metabolite of PGF(2alpha) (15-keto-13,14-dihydro-PGF(2alpha)) and progesterone were investigated during the immediate, post-partum period in 59 normally calving cows. Uterine involution was monitored by weekly rectal palpations. The levels of the prostaglandin metabolite were high at parturition and remained thereafter elevated for periods varying up to 7-23 days. Uterine involution was completed during periods ranging from 16-53 days. According to the clinical findings, the animals were divided into three groups. Group A comprises 46 animals which had an uncomplicated, puerperal period. A significant (p<0.001) correlation between the duration of elevated prostaglandin levels and the time for completed uterine involution (Y=29.6 - 1.3 (X - 13.5)) was found for these animals. Group B animals (n=8) had periods of varying length with uterine discharge during the first 30 days post-partum. When compared to group A animals, the animals in group B had comparatively longer periods of prostaglandin release and also longer periods for completion of uterine involution. Group C animals (n=5) at times had palpable, thin-walled, cystlike structures in the ovaries during the first 30 days post-partum. In this group of animals, the periods of high prostaglandin levels, as well as for the completion of uterine involution, were similar to those for the animals in group A. Progesterone levels remained low during the immediate post-partum period and in no case were elevated levels found until the prostaglandin release had ceased.

On the control of prostaglandin release during the bovine estrous cycle. Effects of cloprostenol injections.

The study comprise seven cows which were injected i.m. with 500 microgram of a synthetic prostaglandin analogue (cloprostenol) at different stages of their estrous cycles. Peripheral blood plasma levels of progesterone and the main blood plasma metabolite of prostaglandin F2 alpha, 15-keto-13,14-dihydroprostaglandin F2 alpha were determined. The injection of cloprostenol initiated luteolysis in all cases as evidenced by decreasing progesterone levels and occurrence of heat. In two animals injected on days 6 and 12, respectively, of the estrous cycle no release of endogenous prostaglandin F2 alpha was found. In animals injected on day 13 and 15 of their estrous cycles, respectively, a minor but sustained release of prostaglandin F2 alpha was found. In three animals injected on days 17, 17 and 19 of their estrous cycles, respectively, the endogenous release of prostaglandin F2 alpha had already started and no specific effect attributed to the injection of cloprostenol could be observed. It is concluded that the injection of cloprostenol initiates luteolysis with subsequent heat and ovulation. The release of endogenous prostaglandin F2 alpha occasionally seen in conjunction with the induced luteolysis is different and less pronounced as compared to the release seen during normal luteolysis in the cow.

On the control of prostaglandin release during the bovine estrous cycle. Effects of progesterone implants.

Progesterone implants were inserted subcutaneously on day 12 of the estrous cycle in three heifers. The implants were known to release an amount of progesterone sufficient to maintain the peripheral blood plasma at a level of about 1 ng/lm. All three heifers showed luteolysis in a similar way with peaks of 15-keto-13, 14-dihydro-PGF2 alpha of normal magnitude and duration. Concomitantly, progesterone levels declined, but due to the presence of the implants, progesterone was maintained at a level of about 1 ng/ml. The release of prostaglandins, however, continued throughout the experimental period and did not cease until the implants were removed.

Identification and quantitative determination of steroids in bovine corpus luteum during oestrous cycle and pregnancy.

Neutral steroids in bovine corpus luteum were isolated by liquid-gel chromatography on hydrophobic Sephadex, and were analyzed by computerized gas chromatography-mass spectrometry. The presence of progesterone and 20beta-hydroxy-4-pregnen-3-one was confirmed. In addition, 3beta-hydroxy-5-pregnen-20-one, 5-pregnene-3beta,20beta-diol, 3beta-hydroxy-5alpha-pregnan-20-one and 5alpha-pregnane-3beta,20beta-diol were fully identified, and 3-hydroxy-4-pregnen-20-one, 4 pregnene-3,20-diol, 22-hydroxycholesterol and 20,22-dihydroxycholesterol were partially characterized. Steroid sulphates were not detected. Quantification of the six fully identified steroids was based on peak areas in specific fragment ion current chromatograms constructed by the computer. During the 4th-19th day of the oestrous cycle the steroid concentrations varied as follows: progesterone 6.0-36.7 mug/g wet luteal weight, 20beta-hydroxy-4-pregnen-3-one 0.8-5.5 mug/g, 3beta-hydroxy-5-pregnen-20-one 1.0-7.1mug/g, 5-pregnene-3beta,20beta-diol smaller than 0.2-0.9 mug/g, 3beta-hydroxy-5alpha-pregnan-20-one 1.7-8.6 mug/g, and 5alpha-pregnane-3beta,20beta-diol smaller than 0.2-1.2 mug/g. The concentrations of progesterone and 3beta-hydroxy-5-pregnen-20-one seemed to vary in parallel and were low during days 11-17. During this period the concentrations of 5-pregnene-3beta,20beta-diol and 5alpha-pregnane-3beta,20beta-diol were highest as was the relative contribution of all three 20beta-hydroxysteroids to the total amount of steroids. The relative amount of 3beta-hydroxy-5alpha-pregnan-20-one seemed to be highest during days 4-6. The total steroid concentration in corpora lutea taken in early pregnancy (75-105 days) was 18-47 mug/g. In the period 75-90 days, progesterone constituted only 35-42% of the total steroids, 3beta-hydroxy-5alpha-pregnan-20-one as much as 23-40% and the total 20beta-hydroxysteroids 18-30%. The total steroid concentration in corpora lutea taken in midterm and late pregnancy was 21-77 mug/g. In this period progesterone was by far the predominant steroid and constituted about 80-90% of the total steroids in corpora lutea taken between days 150 and 240. Possible correlations between luteal growth, steroid oxidoreductases and steroid concentrations are discussed.