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E. GRUNERT, L. Cl. SCHULZ and J. ESSER

Summary.

Thirty-four cows with `normal' oestrous cycles showed a significant increase in the duration of the cycle following a single intrauterine injection of iodine solution between Day 13 and Day 16. The most distinctive lengthening (average 3·7 days) was observed in animals which had undergone treatment on Day 15. Intrauterine iodine injections from Day 4 to Day 12, on Day 17, and during oestrus did not affect the `normal' oestrous cycle of fifty-three cows.

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J. E. Aurich, I. Dobrinski, H-O. Hoppen and E. Grunert

Concentrations of β-endorphin and oxytocin were measured in plasma of cows before, during and after parturition. The effect of the PGF analogue cloprostenol on β-endorphin and oxytocin release was investigated. During parturition, there were marked, parallel increases in β-endorphin and oxytocin concentrations. Both hormones were released in an episodic manner in conjunction with uterine and abdominal contractions. It is therefore likely that factors stimulating oxytocin release also enhance β-endorphin secretion. This suggests a role of labour or labour-associated hormones in stimulating peripheral β-endorphin release. Cloprostenol caused an immediate, pronounced increase in plasma β-endorphin and oxytocin concentrations.

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J. E. Aurich, I. Dobrinski, H.-O. Hoppen and E. Grunert

Summary. Plasma concentrations of β-endorphin and met-enkephalin were measured, with appropriate radioimmunoassays, in cows during gestation and at parturition and in newborn calves. During pregnancy β-endorphin immunoreactivity (IR) concentration increased, but values during the last month of gestation were not different from those at parturition. Highest met-enkephalin IR levels were obtained in cows during calving. A term Caesarean section caused an increase in plasma β-endorphin and metenkephalin IR concentrations, but no such increase occurred in cases of a preterm Caesarean section. In calves β-endorphin IR values were lower before umbilical cord rupture than immediately after birth. Values decreased continuously thereafter. This was also the case for met-enkephalin IR concentrations in calves born at term. In preterm calves met-enkephalin IR values were low immediately after delivery and increased during the first hour of life. A significant correlation existed between the degree of acidosis and plasma levels of both opioid peptides in the calves. We conclude that a direct stimulation of peripheral β-endorphin release by the pain or stress associated with calving does not seem to exist in cattle, whereas met-enkephalin seems to be more directly related to parturition. In calves the change to the extrauterine environment causes an immediate, increased release of both opioids.

Keywords: β-endorphin; met-enkephalin; cattle; parturition; neonate

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M. A. Mena, G. Grunert, M. S. Mansilla, M. E. Lúcia, M. I. Pizarro, P. A. Hidalgo and A. N. Tchernitchin

Summary. Testosterone propionate (50 mg/kg), administered together with oestradiol, inhibited the oestrogen-induced uterine eosinophilia, deep endometrial oedema and the increase in uterine wet weight, 6 h after treatment. The same dose of the androgen decreased the number of eosinophils in the blood and increased their degranulation, explaining the effect of testosterone in the uterus. The high doses of the androgen used were in the range of the doses reported by others to block selectively the oestrogen-induced increase in uterine peroxidase content but not other responses to oestrogen or the cytosolic oestrogen receptor translocation to the nucleus. The dissociation by high doses of testosterone of the oestrogen-induced uterine eosinophilia, wet weight increase and oedema from other responses to oestrogen in the absence of any measurable effect of testosterone upon cytosolic—nuclear oestrogen receptors supports the idea that uterine eosinophilia and oedema are oestrogenic responses regulated by mechanisms different from those of the genomic responses, and is in agreement with the hypothesis of the mediation of uterine oedema by eosinophils.