Effects of luteotrophic and luteolytic hormones on expression of mRNA encoding insulin-like growth factor I and growth hormone receptor in the ovine corpus luteum

Abstract

The regulation of mRNAs encoding insulin-like growth factor I (IGF-I) and the receptor for growth hormone (GH-R) in ovine luteal tissue by luteotrophic and luteolytic hormones was examined. In Expt 1, ewes were hypophysectomized (HPX) on day 5 of the oestrous cycle and administered saline (S), LH, GH, or LH + GH until day 12 of the oestrous cycle (n = 4 ewes per group). Concentrations of luteal mRNA encoding IGF-I in HPX + S ewes and pituitary-intact ewes at day 5 (n = 4) were approximately 60% (P < 0.05) of those in pituitary-intact ewes at day 12 (n = 4). Treatment of HPX ewes with GH or GH + LH, but not LH alone, increased concentrations of mRNA encoding IGF-I to values similar to those in pituitary-intact ewes at day 12. Hypophysectomy also reduced the mean concentration of mRNA encoding GH-R to approximately 60% (P < 0.05) of the values in pituitary-intact ewes (days 5 or 12). Treatment with LH, but not GH, increased (P < 0.05) concentrations of mRNA encoding GH-R to values observed in pituitary-intact ewes. In Expt 2, prostaglandin F2 alpha (PGF2 alpha; 1 mumole) injected into the ovarian artery on day 11 or day 12 of the oestrous cycle had no effect on luteal concentrations of mRNA for either IGF-I or GH-R. In Expt 3, concentrations of mRNA encoding IGF-I increased (P < 0.05) between days 3 and 6 and remained high for the duration (days 9, 12 and 15) of the oestrous cycle while luteal concentrations of mRNA encoding GH-R did not change. In conclusion, responsiveness of the corpus luteum to GH and luteal synthesis of IGF-I are likely regulators of luteal development and function. However, PGF2 alpha-induced luteolysis was not associated with a decrease in concentrations of mRNAs encoding either IGF-I or GH-R.

Growth hormone and insulin-like growth factor-I action on progesterone secretion by porcine corpora lutea isolated at various periods of the luteal phase

“…Indeed, in the ewe, GH supports IGF expression in the luteal tissue (Juengel et al, 1997). Receptors for IGF-I have been demonstrated in luteal tissues of several species including the rat (Talavera and Menon, 1991;Parmer et al, 1991), cow (Sauerwien et al, 1992), human (Obasiolu et al, 1992) and ewe (Perks et al, 1995).…”

“…In the early 1990s receptors for GH or mRNA encoding GH receptor were identified in bovine (Lucy et al, 1993), rat (Carlsson et al, 1993) and ovine (Juengel et al, 1997) luteal tissue. Although a number of physiological studies have implicated GH in altering ovarian function in cows, rats and ewes, there are relatively few data concerning pigs (Hsu and Hammond, 1987;Yuan and Lucy, 1996;Xu et al, 1997;Gregoraszczuk et al, 2000).…”

Comparative Activities of Growth Hormone and Luteinizing Hormone in the Direct Stimulation of Local Release of Progesterone from Microdialyzed Ovine Corpora Lutea In Vivo.

“…Recently, the mRNA encoding the GH receptor was shown to be expressed in the ovine cyclic CL [33]. Thus, GH may stimulate the P release via a receptor-mediated pathway.…”

Growth hormone and growth hormone gene of the American mink (Neovison vison) – the current state of knowledge of one of the key hormones in one of the most intensively economically exploited species

“…It should be noted that in the case of the reproductive system of females, GH can show the effects on the endocrine path, through pituitary somatotropin, as well as auto-, para-or intracrine, through the hormone produced locally in the ovary (Schwärzler et al, 1997). The presence of receptors for GH was shown in the luteal tissue in many mammal species, where it stimulates secretion of progesterone (P 4 ) and maintains the function of the corpus luteum (Carlsson et al, 1993;Liebermann, Schams, 1994;Juengel et al, 1997). The stimulation of the increase of proliferation and uterine cells has also been shown (Gunin, 1997).…”