CHANGES OF PROGESTERONE, TOTAL OESTROGENS, CORTICOSTEROIDS, PROLACTIN AND LH IN BOVINE PERIPHERAL PLASMA AROUND PARTURITION WITH SPECIAL REFERENCE TO THE EFFECT OF EXOGENOUS CORTICOIDS AND A PROLACTIN INHIBITOR RESPECTIVELY

Abstract

ABSTRACT Plasma samples from jugular vein blood of cows before, during and after normal or glucocorticoid induced parturition and also in cases treated with a prolactin inhibitor were collected. Total oestrogens, prolactin and LH were determined by radioimmunological techniques, corticoids by competitive protein binding and for progesterone analysis both techniques were used. Progesterone began to decrease 1–2 day before parturition while the corticoid values increased concomitantly. The oestrogen levels remained high, almost until parturition had occurred; they began to decrease very rapidly approximately 5 hours before delivery. Prolactin showed the expected peak just before delivery and LH was constantly low. In the animals treated with a synthetic glucocorticoid or the prolactin inhibitor a temporary suppression of endogenous corticoids or of prolactin resp. was observed; no significant differences could be seen in the values of the other hormones and the physiological performance as compared to a normal delivery. It is concluded that a possible synergistic action of oestrogens and glucocorticoids is involved in the termination of pregnancy in the bovine species.