Progesterone and 15-keto-13, 14-dihydroprostaglandin F2alpha levels in peripheral circulation after intrauterine iodine infusions in cows

The effect of intrauterine iodine infusion on estrous cycle length was studied in four cows. The infusions were performed at various times of the estrous cycle: early, middle, late, and during luteolysis. Blood samples were drawn every third hour from the jugular vein. Progesterone and 15-keto-13,14-dihydroprostaglandin F_2α (the main metabolite of PGF_2α) were measured to monitor luteal activity and prostaglandin release. No release of prostaglandins was observed immediately following intrauterine infusion. Infusion in two cows on day 5 of the estrous cycle resulted in prostaglandin release after 54 and 69 hrs., respectively, followed by luteal regression and the occurrence of estrus at approx. five days after infusion. Infusions performed on days 11 or 12 resulted in prostaglandin release after 147 and 120 hrs., respectively, followed by luteolysis and heat after a 19 day estrous cycle. Infusion in two cows at days 16 and 17 resulted in prostaglandin release after 117 hrs. in both animals. One cycle was prolonged whereas the other cycle was normal in duration. One cow infused on day 20 following the occurrence of the first prostaglandin surge had a cycle length of 26 days, whereas another cow infused on day 20 was not affected because luteolysis was essentially complete by the time of infusion. One animal infused on day 5 did not respond to the iodine infusion. In this animal, however, the corpus luteum was not completely developed prior to the infusion.From this study it can be concluded: 1) intrauterine iodine infusions performed after the development of a progesterone secreting corpus luteum result in prostaglandin release within three to six days with the subsequent occurrence of luteolysis; 2) luteolysis w^ras in all cases observed in connection with prostaglandin F_2α release of the same order of magnitude and duration as during normal luteolysis. kw|Keywords|k]prostaglandin release; k]progesterone; k]cow; k]es trous cycle; k]iodine infusion     

Prostaglandin Release at Dexamethasone Induced Parturitions in Cows

Three cows of the Swedish Red and White Breed (SRB) were used in the experiment. Cow no. 1 pregnant for 247 days, was given 20 mg dexamethasone twice with an interval of 48 hrs. Cows nos. 2 and 3, each pregnant for 254 days, received 20 mg of dexamethasone twice with an interval of 24 hrs. The cows delivered normal living calves 153, 138 and 137 hrs., respectively, after the second injection of dexamethasone. Blood samples were drawn from the jugular vein every third hour during the experimental period and the samples were analyzed for estrone, progesterone and 15-keto-13,14-dihydroprostaglandin F₂α. Following the dexamethasone injections there was a continuous increase in the blood plasma levels of estrone followed by a sharp decrease in conjunction with parturition. The blood plasma level of progesterone showed a slow but continuous decrease until about 24 hrs. before delivery when a marked drop occurred. The levels of the prostaglandin metabolite increased gradually until about 24 hrs. prior to delivery. This was followed by an abrupt rise, and high levels of the prostaglandin metabolite were recorded for up to four days following parturition. It is concluded that the estrone increase preceded that of the prostaglandin metabolite and that the final drop in the progesterone was synchronous with the final rise of the prostaglandin metabolite level.     

Plasma cortisol in the horse, diurnal rhythm and effects of exogenous ACTH.

Peripheral blood plasma Cortisol concentration and its diurnal variation was measured in 4 horses. Mean concentration of Cortisol during 24 hrs. was 42 ng/ml (s ± 20 ng/ml). Peak values occurred at 6 a.m. and the lowest values were observed at about 6 p.m. (mean 65 ng/ml and 20 ng/ml, respectively).Long-acting ACTH at a dose of 150 i.u. was given by intramuscular injection to the 4 horses. Peak Cortisol concentrations markedly exceeding the prestimulation level were obtained between 2 and 4 hrs. after injection. During the immediate 24 hrs. after these peaks, the mean Cortisol level was markedly lower and the cyclic variation out of phase with the basal diurnal pattern. After a gradual adjustment during the second postinjection day, no differences could be seen between the 2 patterns on day 3 after injection.     

Changes in Plasma Progesterone Levels During Storage of Heparinized Whole Blood from Cow,Horse, Dog and Pig

Progesterone concentrations in heparinized plasma harvested immediately after blood collection were compared with levels obtained after storage of the corresponding whole blood for 2 h, 4 h, 6 h, 1 day, 2 days and 5 days at room temperature and in a refrigerator. The blood was taken during the luteal phase from 4 dogs, 4 horses, 4 pigs and 8 cows. For 4 cows the storage time was extended to 9 and 20 days. No significant effect of whole blood storage time on plasma progesterone concentrations could be shown for dogs or pigs. For the horse a slight but significant decrease was demonstrated when the blood was kept at room temperature. For the cow, however, a dramatic decrease was observed even when the blood was stored in the refrigerator. Following incubation of cow’s blood at room temperature, progesterone levels were close to zero after 1–2 days. By further extending the storage period, a reappearance of assayable progesterone could be elicited. For all species it was found that the storage of plasma at room temperature for 5–9 days did not change the progesterone concentrations.