Prostaglandin induced early abortions in the bovine. Clinical outcome and endogenous release of prostaglandin F2α and progesterone

Animal Reproduction Science, 3 (1980/1981) 289--299

289

Elsevier Scientific Publishing Company, Amsterdam - - P r i n t e d in The Netherlands

PROSTAGLANDIN INDUCED EARLY ABORTIONS IN THE BOVINE. CLINICAL OUTCOME AND ~ E N O U S RELEASE OF PROSTAGLANDIN F2~ AND PROGESTERONE 1

JAN-OTTO LINDELL*, HANS KINDAHL* and LARS-ERIC EDQVIST**

*Department of Obstetrics and Gynaecology and **Department of Clinical Chemistry, Swedish University of Agricultural Sciences, S-750 07 Uppsala (Sweden) 1This investigation was supported by the Swedish Council for Forestry and Agricultural Research. (Accepted 14 August 1980)

ABSTRACT

LindeU, J.-O.,Kindahl, H. and Edqvist, L.-E., 1981. Prostaglandin induced early abortions in the bovine. Clinicaloutcome and endogenous release of prostaglandin F2a and progesterone. Anim. Reprod. Sci.,3: 289--299. Peripheral blood plasma levels of progesterone and the main blood plasma metabolite of prostaglandin F~a (15-keto-13, 14-dihydro-PGF2a ) were analysed in 12 heifers in which abortions were induced with a prostagiandin analogue (cloprostenol) at pregnancy stages from 39--146 days. All animals except one (treated on day 75 of pregnancy) aborted within 4 days following treatment. The peripheral plasma levels of progesterone decreased rapidly following the injection of cloprostenol. All heifers had shortlasting peaks of the prostaglandin metabolite in connection with luteal regression. In animals pregnant for less than 80 days this release ceased at the time of delivery of the fetuses, which were expelled within unruptured fetal membranes. Standing estrus was observed in connection with the expulsion of the fetuses. Two of the animals were mated at this estrus and became pregnant. In contrast, animals pregnant for more than 100 days released massive amounts of prostaglandin F2a during a 2--5-days period post partum and had retained fetal membranes. No heat was observed in connection with these abortions. The animal that failed to abort showed no change in the prostaglandin metabolite levels.

INTRODUCTION

Normal parturition in the cow is preceded by an abrupt drop in the peripheral blood plasma concentration of progesterone occurring simultaneously with increased release of prostaglandin F2a (PGF2~) (Fairclough et al., 1975; Edqvist et al., 1978). Exogenous administration of PGF2a to pregnant cows causes regression of the corpus luteum (Lauderdale, 1972; Lamond et al., 1973). Consequently the immediate prepartum progesterone drop is considered to reflect the luteolytic action of PGF2~ released at this time. The POF2a release in conjunction with parturition continues for about 10--20 0378-4320/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company

290 days after delivery (Edqvist et al., 1978). A similar pat t ern of PGF2~ release is also seen following dexamethasone-induced parturition in the late pregnant cow (Lindell et al., 1977). The physiological role of this sustained release of prostaglandin F2~ is not well understood. Previous studies reporting on the profile o f th e peripartum PGF2~ release have all been carried out in the late pregnant cow. In the present study an investigation is made of the PGF:~ release patterns as well as of the progesterone concentrations at the time of induced deliveries in cows at early stages o f pregnancy. MATERIALS AND METHODS

Animal experiment Twelve heifers (nos. 1--12) of the Swedish Red and White Breed (SRB) were used. The age of the animals varied from 10 to 14 m o n t h s on arrival at the e x p e r i m e n t station. The heifers were subjected to clinical investigations including rectal and vaginal examinations in order t o establish t h a t t h e y were normally developed and exhibited normal estrous cyclicity. After three regular estrous cycles the heifers were m at ed with a bull. The animals were rectally examined 4--5 weeks after mating in order t o verify pregnancy. When pregnancy was established the animals were left undisturbed until participating in the present study. Th e heifers were injected with 500 pg o f a prostaglandin analogue (cloprostenol, Estrumate ® , I.C.I.) in order t o induce luteolysis and subsequent abortion. The injections were given at different stages of pregnancy (days 39-TABLE I Some clinical observations on the animal material Animal Days between conception and no. injection abortion

Group I 1 2 3 4 5

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Length of the subsequent estrous cycle(s) (days) pregnant pregnant 21 21 14

39 39 58 60 71

41 41 61 62 74

60 55 72 53 68

Group II 7 102 8 116 9 123 10 132 11 140 12 146

105 120 127 135 144 149

86 88 91 60 91 78

2 2 2.5 2.5 3 18 24 14 24 29 36

12, 10, 21 21 8 not determined not determined not determined

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146, see Table I). After abortion the ovarian status of some animals was checked daily by rectal palpation. All fetuses were submitted to macroscopic autopsy. Blood samples were drawn from the jugular vein every 3 h between 2--5 days prior to injection and 1 - 6 days following abortion and in some animals for up to 19 days. Blood samples were collected into heparinized tubes (Vacutainer ® system, Becton and Dickinson) which were immediately centrifuged. The plasma was removed and stored in plastic tubes at --20°C until analyses were performed. A naly tical me thods

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Standing estrus was observed within 3 days following injection to all heifers in group I. Two of the heifers in this group (nos. 1 and 2) were mated once at this estrus, 74 and 77 h post injection, respectively, and became pregnant. The other three heifers (nos. 3--5) had a subsequent estrous cycle of 21, 21 and 14 days, respectively (Table I). In the group II heifers (nos. 7--12) no sign of standing estrus was observed until days 18, 24, 14, 24, 29 and 36, respectively, post injection. Growing follicles were palpated for. 1--3 days following abortion in all group I heifers. In the group II heifers follicles were palpated in nos. 7 and 9, but these follicles did not ovulate and grew slowly firmer during a 7-days period. The other animals in group II were not examined post abortion for the presence of follicles. In animals nos. 7 and 9 shortlasting luteal phases were detected during the immediate post-partum period. These luteal phases lasted for 7 to 9 days and were terminated in connection with shortlasting peaks of the prostaglandin metabolite (Fig. 3, upper and lower panel). After this luteolysis the animals showed heat which occurred at days 18 and 14, respectively, post injection. In these two heifers the next observed heat occurred 12 and 8 days later. Before injection of cloprostenol the blood plasma levels of progesterone in the heifers of both groupsvaried from 6 to 40 nmol/1 (Figs. 1--4). Following injection all animals, except no. 6, lowered their progesterone levels to below 1 nmol/1 within 2 days and these animals aborted their fetuses between 53 and 91 h after injection. In the animal (no. 6), which did not abort, the progesterone concentration fell from about 7--15 nmol/1 to about 3--5 nmol/1. Thereafter the progesterone level increased slowly and irregularly during the 10-days period of sampling. Animals pregnant for less than 80 days (group I) released shortlasting peaks of 15-keto-13,14-dihydro-PGF2~ following injection. These elevated levels returned below the pretreatment levels at the time of expulsion of the fetus. Similar patterns were seen in animals pregnant for more than 100 days at the time of injection (group II). However, these animals released massive amounts of 15-keto-13,14
Fig. 3. Blood levels of 1 5 - k e t o - 1 3 , 1 4 - d i h y d r o - P G F ~ (o o ) and progesterone (* . . . . *) in heifers no. 7 (upper panel), no. 8 (middle panel) and no. 9 (lower panel). D o t t e d arrow indicates time of cloprostenol administration, and the solid arrow denotes time of abortion.

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Fig. 4. B l o o d levels of 15-keto-13,14-dihydro-PGF2a (o o) and progesterone (e . . . . e) in heifers no. 10 (upper left), no. 11 (upper right) and no. 12 (lower panel). D o t t e d arrow indicates time of cloprostenol administration, and the solid arrow denotes time of abortion. DISCUSSION

In the present study the prostaglandin analogue was used to induce luteolysis because it does not cross-react in the assay system for the prostaglandin metabolite (15-keto-13,14-dihydro-PGF2~) and thus allows an estimation of endogenously released prostaglandin F ~ (Kindahl et al., 1980). This is further verified by the lack of increase in the prostaglandin metabolite level following the administration of cloprostenol to heifer no. 6. The progesterone drop following the injection of the prostaglandin analogue accords with previous results demonstrating the luteolytic effect of prostaglandin F2~ in pregnant cows (Lauderdale, 1972; Lamond et al., 1973).

297 All heifers which aborted had some pulsatile endogenous prostagiandin release immediately following injection of cloprostenol. The nature of this release is not known. In cycling ewes a release of endogenous P G F ~ has also been reported after injection of cloprostenol (Challis et al., 1976). These authors suggested that the withdrawal of progesterone could be a stimulus for prostaglandin synthesis and secretion from the uterus. However, in the bovine no endogenous prostaglandin release is seen following injections of cloprostenol or manual enucleation of the corpus luteum during the first 12--14 days of the estrous cycle, while the same treatment applied at later stages in the cycle causes a small release of prostaglandin although less pronounced than that produced during normal luteolysis (Kindahl et al., 1980). The difference in the prostaglandin release between cycling and pregnant cows might be that during early pregnancy the corpus luteum function is maintained due to a block of prostaglandin synthesis and/or release initiated by the presence of the fetus (Kindahl et al., 1976b). It might be assumed that this block is maintained at least during early pregnancy. An explanation for the endogenous prostaglandin release shortly after the injection of the analogue might be that the injected prostaglandin abolishes this block, e.g. by causing myometrial contractions and disrupting the delicate connection between fetal and maternal tissues. The post-abortion release of PGF2a in the animals delivering at pregnancy stages of more than 80--100 days mimics the release seen in cows calving at the expected time (Edqvist et al., 1978), although the duration of the former release is shorter. This difference in the post~bortion PGF2~ release between animals aborting at pregnancy stages before and after about 80 days is probably due to a difference in physical connection between the chorion and the caruncles of the endometrium. Thus the fetuses in group I were all aborted within unruptured fetal membranes and without sign of blood. The cotelydons were, however, visible as small reddish areas. It is known that the mechanism of fetal attachment in the bovine is a relatively slow procedure (Chang, 1952; King et al., 1979). According to these authors a faint disc~haped tissue (cotelydon) appears on the chorion at the sites of the caruncles at about 40 days of pregnancy. Kingman (1951), furthermore, stated that the chorion is self~upporting up to about 70 days and thus the physical connection up to about this stage is a delicate one. The occurrence of discharge containing blood and retained fetal membranes in animals aborting at late pregnancy stages (~100 days) indicates a firmer connection between fetal and maternal tissues. The massive post~lelivery release of PGF2~ in these animals might be due to the more severe uterine trauma. It is also probable that this release aided in the expulsion of the fetus by causing myometrial contractions. In the early abortions (~80 days) no pronounced release was seen in conjunction with the abortions or thereafter. These animals showed heat simultaneously with abortion and it is likely that the uterine contraction occurring as a consequence of the estrus aided in the expulsion of the fetus. The occurrence of estrus in these heifers and the

298 establishment of pregnancy in two of the animals further support the idea that these abortions were associated with only mild uterine trauma. The physiological significance of the massive post-abortion release following the late abortions is not known. However, it has been shown that exogenously administered PGF2~ to heifers causes release of prolactin (Louis et al., 1974). Thus the massive postpartum PGF2~ release might be of importance for initiation of lactation. Furthermore, in cows delivering normally at the expected time, the duration of the postpartum PGF2~ release correlates to the period required for completing uterine involution in such a way that cows with long involution periods had a comparatively shorter duration of the prostaglandin F2~ release (LindeU et al., 1980). In heifers nos. 7 and 9, which were rectally palpated during the post-abortion period, growing follicles were found. These follicles were not ovulated but were slowly luteinized. This is supported by simultaneously occurring elevations of the progesterone concentrations in blood. The resulting luteal phases were short and terminated in association with shortlasting elevations of the 15-keto-13,14
299 REFERENCES Challis, J.R.G., Forster, C.S., Furr, B.J.A., Robinson, J.S. and Thorburn, G.D., 1976. Production of PGF=a in ewes following lutes] regression induced with a prostaglandin analogue, estrumate (cloprostenol; I.C.I. 80996). Prostaglandins, 11: 537--543. Chang, M.C., 1952. Development of bovine blastocyst with a note on implantation. Anat. Rec., 113: 143--162. Copeland, P.D., Schultz, R.H. and Remtrup, M.E., 1978. Induction of abortion in feedlot heifers with cloprostenol (a synthetic analogue of prostaglandin F2a): A dose response study. Can. Vet. J., 19: 29--32. Edqvist, L.-E., Settergren, I., Swensson, I. and Astr~m, G., 1974. Symposium on egg transplantation. The Assoc. for Swedish Livestock Breeding and Production (SHS), H~llsta, S-631 84 Eskilstuna, Sweden, Publ. no. 75: 61--85. Edqvist, L.-E., Kindahl, H. and Stabenfeldt, G., 1978. Release of PGF2a during the bovine peripartal period. Prostaglandins, 16: 111--119. Falrclough, R.J., Hunter, J.T. and Welch, R.A.S., 1975. Peripheral plasma progesterone and utero-ovarian prostaglandin F concentrations in the cow around parturition. Prostaglandins, 9: 901--914. Kindahl, H., Edqvist, L.-E., Granstr~im, E. and Bane, A., 1976a. The release of PGF2a as reflected by 15-keto-13,14-dihydro-PGF~a in the peripheral circulation during normal luteolysis in heifers. Prostaglandins, 11: 871--878. Kindahl, H., Edqvist, L.-E., Bane, A. and Granstr~m, E., 1976b. Blood levels of progesterone and 15-keto-13,14-dihydro-PGF2a during the normal oestrous cycle and early pregnancy in heifers. Acta Endocrinol. (Copenhagen), 82: 134--149. Kindahl, H., Edqvist, L.-E., and Lindell, J.-O., 1980. On the control of prostaglandin release during the bovine estrous cycle. In: B. Samuelsson, P.W. Ramwell and R. Paoletti (Editors), Advances in Prostaglandin and Thromboxane Research. Raven Press, N e w York, NY, Vol. 8, pp. 1351--1355. King, G.J., Hurnik, J.F. and Robertson, H.A., 1976. Ovarian function and estrus in dairy cows during early lactation. J. Anim. Sci., 42: 688--692. King, G.J., Atkinson, B.A. and Robertson, H.A., 1979. Development of the bovine placentome during the second month of gestation. J. Reprod. Fertil., 5 5 : 1 7 3 - - 1 8 0 . Kingman, H.E., 1951. Implantation of the fertilized ovum and its relation to the infertility problems in the cow. Proc. Nation. Egg Transfer Breeding Conference, San Antonio, U.S.A., 1951, pp. 26--29. Lamond, D.R., Tomlinson, R.V., Drost, M., Henricks, D.M. and J~chle, W., 1973. Studies of prostaglandin F2a in the cow. Prostaglandins, 4: 269--284. Lauderdale, J.W., 1972. Effects of PGF~a on pregnancy and estrous cycles of cattle. J. Anita. Sci., 36 : 246--249. Lindell, J.-O., Kindahl, H. and Edqvist, L.-E., 1977. Prostaglandin release at dexamethasone induced parturitions in cows. Acta Vet. Scand., 18: 257--265. Lindell, J.-O., Kindahl, H. and Edqvist, L.-E., 1980. Uterine involution in relation to postpartum release of PGF2a in the cow. Proc. Int. Congr. Anim. Reprod. and A.I., Madrid~ III: 155. Louis, T.M., Stellflug, J.N., Tucker, H.A. and Hafs, H.D., 1974. Plasma prolactin, growth hormone, luteinizing hormone and glucocorticoids after prostaglandin F2~ in heifers (38295). Proc. Soc. Exp. Biol. Med., 147: 128--133. Morrow, D.A., Roberts, S.J., McEntee, K. and Gray, H.G., 1966. Post-partum ovarian activity and uterine involution in dairy cattle. J. Am. Vet. Med. Assoc., 149: 1596--1609. Morrow, D.A., Roberts, S.J. and McEntee, K., 1969. A review of post-partum ovarian activity and involution of the uterus and cervix in cattle. Cornell Vet., 59: 134--154. Powell, S., Hammarstr~m, S. and Samuelsson, B., 1975. Occurrence and properties of a prostaglandin F2a receptor in bovine corpora lutea. Eur. J. Biochem., 56: 73--77. Samuel, C., 1977. Physiological and pathological characteristics of the bovine uterus post partum -- a review. Malays. Vet. J., 6: 125--132.