Prolactin Secretion and Ovarian Function in Cycling and Non-Cycling African Female Elephants (Loxodonta africana)

Abstract

ABSTRACT. Reproduction of captive elephants in zoos has shown a low fecundity and requires improvement. One of the reasons for low fecundity is ovarian dysfunction in many female elephants. To investigate whether prolactin has a correlation with ovarian function in female elephants, the serum concentrations of prolactin, progesterone and estradiol-17 in four African female elephants (one cycling female and three non-cycling female elephants) were measured. Cyclic patterns of prolactin and estradiol-17 were observed in the cycling female elephant, which tended to be high during the follicular phase and low during the luteal phase. On the other hand, a cyclic pattern of prolactin was not observed in the non-cycling female elephants. One of the three non-cycling females (Mako) had developed breasts and showed significantly higher average levels of prolactin than the other female elephants. These results suggested that high concentrations of circulating estradiol-17 during the follicular phase stimulated prolactin secretion. They also suggested that hyperprolactinemia in Mako was one of the causes of the developed mammary glands and ovarian dysfunction.

The Secretory Pattern and Source of Immunoreactive Prolactin in Pregnant African (<i>Loxodonta africana</i>) and Asian (<i>Elephas maximus</i>) Elephants

“…Prolactin: Concentrations of PRL in elephant sera and placentae were determined by a heterologous RIA system using an antihuman PRL rabbit sera (NIDDK-anti-hPRL-3, National Institute of Diabetes and Digestive and Kidney Diseases, Torrance, CA, USA), iodinated ovine PRL (NIDDK-oPRL-I-2), ovine PRL standard (NIDDK-RP-2) and goat anti-rabbit gamma globulin (ARGG) as previous described [22]. Thus, PRL levels are referred to as immunoreactive (ir-) PRL in the present paper.…”

“…The major source of PRL is the anterior pituitary gland, and its major functions during mammalian gestation are development of the mammary glands and stimulation of milk production. PRL secretion is stimulated by several environmental factors including pregnancy, suckling stimulation and stress [2,[6][7][8][9][10][11][12].Reproductive endocrinology including secretion of PRL has been studied in elephants previously [13][14][15][16][17][18][19][20][21][22]. However, many mysteries, such as the source and the function of PRL during pregnancy, still remain.…”

“…Reproductive endocrinology including secretion of PRL has been studied in elephants previously [13][14][15][16][17][18][19][20][21][22]. However, many mysteries, such as the source and the function of PRL during pregnancy, still remain.…”

Seasonality of reproduction in Asian elephantsElephas maximusand African elephantsLoxodonta africana: underlying photoperiodic cueing?

“…Several authors found acyclicity to be related to hyperprolactinemia (Yamamoto et al. , Brown et al. ) and levels of prolactin were found to be positively correlated with cortisol levels in captive African elephants (Bechert et al.…”

“…While the majority of publications on zoo elephants focus on acyclicity and potential causes (Yamamoto et al. , Glaeser et al. , Brown et al.…”