Plasma Profiles of Growth Hormone, Prolactin and Insulin-like Growth Factor-I during Gestation, Lactation and the Neonatal Period in Goats.

Abstract

Abstract. The objectives of this research were to characterize plasma profiles of growth hormone (GH), prolactin (PRL) and insulin-like growth factor-I (IGF-I) during gestation and the lactation period in goats, as well as in their suckling growing kids. There were no obvious changes in the GH or PRL profiles during gestation, but secretion of both GH and PRL increased acutely after parturition. The elevated GH concentrations were maintained until 3 months after parturition, whereas the PRL concentrations decreased gradually after parturition. The elevated hormone concentrations are thought to be caused mainly by an increase in the secretory pulse amplitudes. In contrast to the GH and PRL profiles, the plasma IGF-I concentrations during late gestation were significantly higher than the post-parturition concentrations, and the IGF-I concentrations in late gestation decreased gradually until the day of parturition. The plasma GH, PRL and IGF-I concentrations in kids 1 week after birth were high, and concentrations of each hormone decreased thereafter. These results show that the increased secretory potencies of pituitary GH and PRL after parturition are caused mainly by an increase in the secretory pulse amplitudes and that plasma GH is inversely related to plasma IGF-I compared over gestation and the lactation period in goats. Key words: GH, PRL, IGF-I, Gestation, Lactation.(J. Reprod. Dev. 45: [273][274][275][276][277][278][279][280][281] 1999) G estation is a composite of integrated processes, resulting in the successful development of fetuses and the birth of offspring. The energy and nutrient requirements in pregnant animals are increased during gestation [1]. The survival of newborn animals is dependent on an adequate supply of milk secreted from the mammary glands of the mother after parturition [2]. Since growth hormone (GH) regulates many aspects of metabolic activity [3], it is meaningful to examine the GH profiles throughout gestation and during the lactation period in animals. Plasma or serum concentrations of GH and prolactin (PRL) in ruminants have been observed to elevate acutely during the periparturient period [4][5][6][7][8][9]. In these published observations, however, blood samples were usually collected for only a few weeks around parturition, and plasma profiles of GH and PRL have never been examined throughout gestation. Moreover, the blood samples were collected only about once a day, although GH and PRL are known to be secreted in transient pulses [3,[10][11][12][13][14]. PRL is required for the initiation of lactation [15,16]; therefore, it is of interest to determine how the pulsatile secretory patterns of both GH and PRL change throughout gestation and during the lactation period in animals. The anabolic action of GH is

Characteristics of the Stimulatory Effect of Kisspeptin-10 on the Secretion of Luteinizing Hormone, Follicle-Stimulating Hormone and Growth Hormone in Prepubertal Male and Female Cattle

“…Plasma LH, FSH and GH concentrations were measured by a double-antibody RIA procedure with slight modifications [24,25].…”

Immunoreactive Insulin-Like Growth Factor in Plasma during Pre- and Post-Partum Periods of Thoroughbred Mares from which the Newborn were Removed: its Pattern, Physiological Function and Relation to Other Hormones

“…Hashizume et al [4] suggested that as the stages of pregnancy are considered anabolic for the dam with i n c r e a s e d p r o t e i n a n d f a t d e p o s i t i o n , h i g h concentrations of IGF-I may play an important role in supporting metabolism during pregnancy in animals and stimulate fetal growth by activating the placental transport of nutrients to the fetus. The ir-IGF-I level in the present work showed a similar pattern to the results of Hess-Dudan et al [5].…”

“…Plasma IGF-I concentrations were measured by a double-antibody RIA procedure [10] as described in a previous paper [4]. Levels of immunoreactive (ir-) inhibin, follicle stimulating hormone (FSH), luteinizing hormone (LH), equine chorionic gonadotrophin (eCG), estradiol-17β (E 2 ) and progesterone (P 4 ) in peripheral blood were measured by RIA as described in previous papers [2,4].…”

“…e-mail. derar40@hotmail.com s i g n i f i c a n t l y h i g h e r t h a n t h e p o s t -p a r t u m concentration, with the IGF-I level in late gestation decreasing gradually until the day of parturition [4]. IGF-I may play an important role in maintaining lutealgranulosa cell function in the absence of a constant FSH stimulus [7].…”

Insulin-Like Growth Factor-I as a Follicular Growth Promoter during Early Pregnancy in Thoroughbred Mares

“…However, its role and source after luteinization and/or ovulation of these follicles is still to be investigated. It was suggested that maternal IGF-I stimulated by activating the placental transport of nutrients [7], and the IGF-I was shown to be adjunctively and directly associated with fetal growth in human [20]. However, it was reported that there was a loss of the relationship between fetal weight and maternal plasma IGF-I concentrations in sheep [8].…”