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Parturition and Lactation in the Bitch: Serum Progesterone, Cortisol and Prolactin

1978; Oxford University Press; Volume: 19; Issue: 5 Linguagem: Inglês

10.1095/biolreprod19.5.1113

1529-7268

Patrick W. Concannon, W.R. Butler, William Hansel, Peter J. Knight, John M. Hamilton,

Neuroendocrine regulation and behavior

Concurrent changes in serum progesterone, cortisol and prolactin associated with the prepartum period and lactation of 6 suckling and 1 nonsuckling Beagle bitches were determined by radioimmunoassay. Progesterone in each bitch fell sharply prior to parturition and remained low during lactation. Mean progesterone at approximately 120, 36, 20 and 10 h prepartum was 4.5 ± 0.6, 3.1 ± 0.4, 1.2 ± 0.4 and 0.6 ± 0.1 ng/ml, respectively. In 6 of 7 bitches, serum cortisol was elevated above mean prepartum levels (23 ± 1 ng/ml) during the day prior to the onset of parturition, reached peak levels of 63 ± 7 ng/ml at 8–24 h prepartum and fell to 19 ± 4 ng/ml at 8–12 h postpartum. Mean cortisol remained between 22 ± 1 and 27 ± 5 ng/ml during lactation and weaning. During the last week of pregnancy, serum prolactin levels (14-97 ng/ml) were variable within (50 ± 2 to 33 ± 8 ng/ml) and among (25 ± 2 to 80 ± 9 ng/ml) bitches and averaged 40 ± 7 ng/ml. In each bitch, prolactin increased by 195 ± 29% during the 16–56 h prepartum and reach peak levels (117 ± 24 ng/ml) at 8–32 (21 ± 3) h prepartum in 6 bitches and at 24 h postpartum in the remaining bitch. By 36 h after these peaks, prolactin levels were reduced to 37 ± 8 ng/ml before again increasing in response to suckling. Mean prolactin increased during the first week of lactation, peaked at 86 ± 19 ng/ml at 1.5 weeks of lactation, fell slowly to 43 ± 6 ng/ml at 5 weeks, shortly before weaning and then fell abruptly to 13 ± 2 ng/ml following weaning. The hormone changes observed were similar to those reported for several other species and suggest that the bitch may be a useful model for the study of maternal endocrine adjustments.